Building and running programs

Now that you have a module and a source tree with some Go files, you can build or run your program.

How to do it...

• Use go build to build the current package
• Use go build ./path/to/package to build the package in the given directory
• Use go build <moduleName> to build a module
• Use go run to run the current main package
• Use go run ./path/to/main/package to build and run the main package in the given directory
• Use go run <moduleName/mainpkg> to build and run the module’s main under the given directory

Let’s write the main function that starts an HTTP server. The following snippet is cmd/webform/main.go:

package main
import (
    "net/http"
)
func main() {
    server := http.Server{
        Addr:    ":8181",
        Handler: http.FileServer(http.Dir("web/static")),
    }
    server.ListenAndServe()
}

Currently, main only imports the standard library’s net/http package. It starts a server that serves the files under the web/static directory. Note that for this to work, you have to run the program from the module root:

$ go run ./cmd/webform

Always run the main package; avoid go run main.go. This will run main.go, excluding any other files in the main package. It will fail if you have other .go files that contain helper functions in the main package.

If you run this program from another directory, it will fail to find the web/static directory; because it is a relative path, it is resolved relative to the current directory.

When you run a program via go run, the program executable is placed in a temporary directory. To build the executable, use the following:

$ go build ./cmd/webform

This will create a binary in the current directory. The name of the binary will be determined by the last segment of the main package – in this case, webform. To build a binary with a different name, use the following:

$ go build -o wform ./cmd/webform

This will build a binary called wform.