How to use the command goimports (with examples)

The goimports command is a tool provided by the golang.org/x/tools/cmd package that updates Go import lines by adding missing ones and removing unreferenced ones. It is a useful command for ensuring that import statements are organized and up to date in Go projects.

Use case 1: Display the completed import source file

Code:

goimports path/to/file.go

Motivation: When working with Go files, it is important to have correctly imported packages. By running the goimports command on a specific file, you can easily see the completed import source file and ensure that all necessary packages are imported.

Explanation:

• goimports is the command name.
• path/to/file.go is the path to the Go file you want to analyze.

Example output:

package main

import (
	"fmt"
	"log"
	"net/http"
)

Use case 2: Write the result back to the source file instead of stdout

Code:

goimports -w path/to/file.go

Motivation: In certain cases, you may prefer to directly modify the source file rather than just displaying the changes in the console. This flag allows you to automatically update the import statements in the file provided.

Explanation:

• goimports is the command name.
• -w is the flag that tells goimports to write the result back to the source file.
• path/to/file.go is the path to the Go file you want to update.

Example output: The import statements in path/to/file.go will be modified directly.

Use case 3: Display diffs and write the result back to the source file

Code:

goimports -w -d path/to/file.go

Motivation: When dealing with multiple changes in a codebase, it is useful to see the differences between the original import statements and the modified ones. This use case allows you to display the diffs and write the result back to the source file.

Explanation:

• goimports is the command name.
• -w is the flag that tells goimports to write the result back to the source file.
• -d is the flag that tells goimports to display the diffs.
• path/to/file.go is the path to the Go file you want to update.

Example output:

--- path/to/file.go	2021-09-02 14:00:29.111111111 +0000
+++ path/to/file.go	2021-09-02 14:01:37.222222222 +0000
@@ -1,8 +1,7 @@
 package main
 
-import (
-	"fmt"
-	"log"
-	"net/http"
+import "log"
+
+// New imports added by goimports
 
 func main() {

Use case 4: Set the import prefix string after 3rd-party packages

Code:

goimports -local path/to/package path/to/file.go

Motivation: When importing packages from 3rd-party sources, it is common to add a prefix to distinguish them from internal packages. Using this flag, you can set the import prefix string after 3rd-party packages, allowing for better organization of import statements.

Explanation:

• goimports is the command name.
• -local path/to/package is the flag that sets the import prefix string after 3rd-party packages.
• path/to/package is the local package or directory path.
• path/to/file.go is the path to the Go file you want to update.

Example output: The import statements in path/to/file.go will have the import prefix string set after 3rd-party packages.

Conclusion:

The goimports command is a powerful tool for managing import statements in Go projects. Whether you need to display the completed import source file, modify the source file directly, view diffs, or set import prefix strings, goimports provides a convenient way to update your import statements efficiently.