run go/format on generated code

_codegen/main.go

@@ -10,6 +10,7 @@ import (
 	"go/ast"
 	"go/build"
 	"go/doc"
+	"go/format"
 	"go/importer"
 	"go/parser"
 	"go/token"
@@ -77,13 +78,18 @@ func generateCode(importer imports.Importer, funcs []testFunc) error {
 		}
 	}
 
+	code, err := format.Source(buff.Bytes())
+	if err != nil {
+		return err
+	}
+
 	// Write file
 	output, err := outputFile()
 	if err != nil {
 		return err
 	}
 	defer output.Close()
-	_, err = io.Copy(output, buff)
+	_, err = io.Copy(output, bytes.NewReader(code))
 	return err
 }