chore: use goimports as a lib instead of CLI

Author: ldez

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/stretchr/testify v1.11.1
 	golang.org/x/sync v0.17.0
 	golang.org/x/term v0.35.0
+	golang.org/x/tools v0.37.0
 )
 
 require (
@@ -20,6 +21,5 @@ require (
 	github.com/xhit/go-str2duration/v2 v2.1.0 // indirect
 	golang.org/x/mod v0.28.0 // indirect
 	golang.org/x/sys v0.36.0 // indirect
-	golang.org/x/tools v0.37.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

internal/formatter/executable.go

@@ -5,6 +5,8 @@ import (
 	"context"
 	"os/exec"
 	"strings"
+
+	"golang.org/x/tools/imports"
 )
 
 const defaultFormatter = "goimports"
@@ -49,6 +51,14 @@ func (e *Executable) Format(ctx context.Context, src []byte) ([]byte, error) {
 		return src, nil
 	}
 
+	// This is a special case:
+	// Instead of running the `goimports` as a separate process,
+	// call the `imports` package directly.
+	// For compatibility with the existing behavior.
+	if e.cmd == defaultFormatter && len(e.args) == 0 {
+		return imports.Process("", src, nil)
+	}
+
 	return e.exec(ctx, src)
 }