Home > Articles > Programming

A Go Primer

This chapter contains an overview of Go syntax, including declaring variables and functions, looping, creating enumerations, declaring structures, defining methods, implementing interfaces, and casting types.
This chapter is from the book

One of the goals of Go was a consistent and unambiguous syntax. This makes it easy for tools to examine Go programs, and also makes it easy to learn. Unhelpful compiler errors make it difficult to learn a language, as anyone who has made a typo in C++ code using templates will know.

In C, for example, function and global variable declarations have almost the same syntax. This means that the compiler can’t easily tell which one you meant if you make an error. It gives you helpful error messages like “expected ;” on a line where you don’t think a semicolon is expected at all.

The Go grammar was designed to make it possible for the compiler to tell you more accurately what you did wrong. It was also designed to avoid the need to state something that can be easily inferred. For example, if you create a variable and set its value to 42, the compiler could probably guess that this variable should be an integer, without it being explicitly stated. If you initialize it with a function call, then the compiler can definitely tell that the type should be whatever the function returned. This was the same problem that C++ 2011 solves with the auto type.

Go adopts JavaScript’s idea of semicolon insertion, and takes it a step further. Any line that can be interpreted as a complete statement has a semicolon implicitly inserted at the end by the parser.1 This means that Go programs can freely omit semicolons as statement terminators. This adds some constraints, for example enforcing a brace style where open braces are at the end of the line at the start of flow-control statements, rather than on their own. If you happen to be a human, this is unfortunate, because it means that you can’t use the highly optimized symmetry recognition paths, which evolution has spent the last million or so years optimizing in your visual cortex, for recognizing code blocks.

This chapter contains an overview of Go syntax. This is not a complete reference. Some aspects are covered in later chapters. In particular, all of the concurrency-related aspects of Go are covered in Chapter 9, Goroutines.

The Structure of a Go Source File

From: hello.go

1 package main
2 import "fmt"
4 func main() {
5   fmt.Printf("Hello World!\n")
6 }

A Go source file consists of three parts. The first is a package statement. Go code is arranged in packages, which fill the rôles of both libraries and header files in C. The package in this example is called main, which is special. Every program must contain a main package, which contains a main() function, which is the program entry point.

The next section specifies the packages that this file uses and how they should be imported. In this example, we’re importing the fmt package.

Once the fmt package has been imported, any of its exported types, variables, constants, and functions can be used, prefixed by the name of the package. In this simple example, we’re calling Printf(), a function similar to C’s printf, to print “Hello World!” in the terminal.

Although Go uses static compilation, it’s important to realize that import statements are much closer to Java or Python import directives than to C inclusions. They do not include source code in the current compilation unit. Unlike Java and Python packages, Go packages are imported when the code is linked, rather than when it is run. This ensures that a Go application will not fail because of a missing package on the deployment system, at the cost of increasing the size of the executable. Packages in Go are more important than in languages like Java, because Go only provides access control at the package level, while Java provides it at the class level.

When you compile a package (from one or more .go files) with the Gc compiler, you get an object code file for the package. This includes a metadata section that describes the types and functions that the package exports. It also contains a list of the packages that this package imports.

The input to the 6l linker is always a .6 file for the main package. This file contains references to every package that the main package imports, which may in turn reference further packages. The linker then combines them all.

This eliminates one of the most irritating problems with building complex C programs: you include a header, and then have to work out which library provided it and add the relevant linker flags. With Go, if a package compiles, it will link. You don’t have to provide any extra flags to the linker to tell it to link things that you’ve referenced via import directives.

The remainder of a Go file contains declarations of types, variables, and functions. We’ll explore that for the rest of this chapter.

You may find that you have two packages that you want to import that have the same name. This would cause problems in Go. The badStyleImport.go example is functionally equivalent to the example at the start of this section but renames the fmt package, calling it format. Renaming a package when you import it is usually a bad idea, because it makes your code harder for people to read. You should only ever use it when you explicitly need to disambiguate two packages with the same name.

From: badStyleImport.go

0 package main
1 import format "fmt"
3 func main() {
4   format.Printf("Hello World!\n")
5 }

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020