Downloading the Installation Files

The first step is to download the most current version of the installation files. You can find the files on Go's Downloads page at https://go.dev/dl. The instructions shown in Figure 1.1 are for version 1.17.2 for Windows, but you will likely see a more recent version on the page.

Click the link for your operating system in the Featured Downloads section of the page. This will download the necessary installation file or package for your operating system.

Starting the Installation of Go

Once you have downloaded the installation file, open it from your computer. In Windows, you can open it by simply clicking the filename. This will start the Setup Wizard, as shown in Figure 1.2.

Click Next to begin the installation. The next screen displays the End-User License Agreement, as shown in Figure 1.3.

Go is distributed under an open source license. This means that you can modify and/or redistribute the code if you wish, but you must include the same copyright notice in any package you distribute.

You should read through the licensing agreement and then select the check box to accept it. Click Next to continue the installation. The next screen, shown in Figure 1.4, asks you to specify the destination folder where Go will be installed.

You can either accept the default location or set a new location by entering the path to a folder or by clicking on Change to select a new location to install Go. Once you've entered the destination folder, click Next again. On the next screen, click the Install button to start the installation. Note that you might be prompted by Windows asking if you give permission to install the application. If so, you will need to indicate that it is okay.

When the installation is complete, you will see a confirmation message when the installation is complete, similar to what is shown in Figure 1.5. You can click the Finish button to close the wizard.

Compiling and Running the Program

The next step is to compile the file. Compiling is the process of converting human-readable code into machine-readable code. Use the cd command to navigate to the folder where gotest.go is saved:

cd DocumentsGoLang

For our example, we created the file in a subfolder, GoLang, of the Documents folder, so we will change to that folder. If you saved your file in a different folder, then you should navigate to that folder. Figure 1.9 shows the cd command being used in the command prompt window to change to the DocumentsGoLang folder. If you executed the command correctly, you will see the folder name at the end of the prompt.

Compile the program using the following command:

go build gotest.go

Simply enter this command at the command prompt and press Enter. The go build command will compile the file that is included, in this case, gotest.go. It may take a few moments to complete the compile, so as long as you don't see an error message, just wait. Eventually, the prompt will return, as shown in Figure 1.10.

While you don't see anything on the screen, if you list the files in the directory, you should now see that an executable file with an .exe extension called gotest.exe exists.

You can now run the program by entering the program name on the command line and pressing Enter:

gotest

If the program was written and compiled correctly, you will see “Hello, World!” displayed, as shown in Figure 1.11.

Alternate Run Option

The previous steps create and run a separate executable file using your program. The EXE file is useful if you want to share or run the program on a different computer. It is not necessary to create the EXE file if you simply want to test a program and don't plan to use the program somewhere else.

Another option is to compile and run the program in a single step, using this command:

go run program_name.go

You can try this using the same Hello, World! program. Verify that you are still in the correct directory in the command-line window (the directory where the gotest.go file is located) and run the command

go run gotest.go

You should see the following output immediately, without having to run a separate command to execute the program. This is the same output you saw before:

Hello, world!

Troubleshooting Hello, World!

If you had problems with this activity, you may have made one of the common mistakes many people make. Consider the following questions:

• Did you navigate to the correct folder in the command prompt?
• If you are not using the correct folder, you will see a message like the following when you run the go build command:

  C:UsersStudent NameDocuments>go build gotest.go
  can't load package: package gotest.go: cannot find package "gotest.go" in any of:
          c:gosrcgotest.go (from $GOROOT)
          C:UsersStudent Namegosrcgotest.go (from $GOPATH)
  

  Make sure you know where the gotest.go file is located on your computer and navigate to that location using the cd command before compiling and running the program.

• Did you enter the program from Listing 1.1 without any typos or misspellings?
• Most typing errors will be identified when you compile the program. If you see an error after running the go build command, read the error carefully to see where the problem is. As an example, consider the following error:

  gotest.go:3:8: cannot find package "fnt" in any of:
          c:gosrcfnt (from $GOROOT)
          C:UsersStudent Namegosrcfnt (from $GOPATH)
  

  In this example, fmt was misspelled as fnt in the 8th character on line 3 (3:8).

  After correcting the error(s), save the file and try compiling it again.

  Did you enter the commands on the command prompt line correctly?

• Make sure you typed go build without any spelling mistakes. Also make sure you included the .go extension on your program filename.

Formatting Your Go Code

When you entered the code from Listing 1.1, you should have followed the format that was presented, including the spacing and the indentation of the code. Whether you indent with three spaces, four spaces, or a tab will not matter when it comes time to run your program; however, in most job environments there will be posted standards.

By providing consistency in how you format your listings, it makes it easier to go from one listing to the next. Additionally, in organizations with multiple programmers, consistent formatting helps make the code easier to read and maintain.

Unlike many programming languages, Go has tried to reduce the controversy over formatting issues. Debates on whether to use three or four spaces, or to use a tab instead, can all be eliminated by using an included formatting option. You can do the formatting using the go fmt command as follows:

go fmt mycode.go

This will remove or fix minor formatting concerns in mycode.go. Listing 1.2 presents the same “Hello, World!” listing you saw earlier; however, the formatting has been poorly done. Enter this listing and name it gotest2.go.

With the listing created and named gotest2.go, enter the following at the command line:

go fmt gotest2.go

You will see the name of the program displayed when Go has finished running. If you then open gotest2.go in an editor, you will see that the file has been updated with clean formatting:

package main
 
import "fmt"
 
func main() {
     fmt.Println("Hello, world!")
}

Exercise 1.1: Counting Fun

Just as you did with Listing 1.1 in this lesson, enter the code presented in Listing 1.3 in your editor and save it as countingfun.go. Don't worry about the details of how the code works. Rather, focus on entering the code as presented in the listing.

After entering the code in your editor and saving it, use the go run command to run the program:

go run countingfun.go

If you entered the code correctly, you should see the following output:

ctr:  0
ctr:  1
ctr:  2
ctr:  3
ctr:  4
ctr:  5
ctr:  6
ctr:  7
ctr:  8
ctr:  9

If you get an error, try the troubleshooting tips that we presented earlier in this lesson to determine what went wrong.

Exercise 1.2: Counting More Fun

Enter the code from Listing 1.4 and save it with the name morecodingfun.go.

Can you find the changes? Compile and run the program to see the changes in action. When you run the code this time, the output should look like this:

ctr:  0
ctr:  2
ctr:  4
ctr:  6
ctr:  8
ctr:  10
ctr:  12
ctr:  14
ctr:  16
ctr:  18

You can continue to play with the numbers and the text in quotes to see what your changes do. Again, if you have trouble understanding what the code is doing, don't worry; we'll cover that in the rest of the lessons in this book.