feat: add WithUserAgent opt (#156)

dialer.go

@@ -102,15 +102,18 @@ type Dialer struct {
 func NewDialer(ctx context.Context, opts ...Option) (*Dialer, error) {
 	cfg := &dialerConfig{
 		refreshTimeout: 30 * time.Second,
-		sqladminOpts:   []option.ClientOption{option.WithUserAgent(userAgent)},
 		dialFunc:       proxy.Dial,
+		useragents:     []string{userAgent},
 	}
 	for _, opt := range opts {
 		opt(cfg)
 		if cfg.err != nil {
 			return nil, cfg.err
 		}
 	}
+	// Add this to the end to make sure it's not overridden
+	cfg.sqladminOpts = append(cfg.sqladminOpts, option.WithUserAgent(strings.Join(cfg.useragents, " ")))
+
 	// If callers have not provided a token source, either explicitly with
 	// WithTokenSource or implicitly with WithCredentialsJSON etc, then use the
 	// default token source.

options.go

@@ -41,6 +41,7 @@ type dialerConfig struct {
 	refreshTimeout time.Duration
 	useIAMAuthN    bool
 	tokenSource    oauth2.TokenSource
+	useragents     []string
 	// err tracks any dialer options that may have failed.
 	err error
 }
@@ -83,6 +84,13 @@ func WithCredentialsJSON(b []byte) Option {
 	}
 }
 
+// WithUserAgent returns an Option that sets the User-Agent.
+func WithUserAgent(ua string) Option {
+	return func(d *dialerConfig) {
+		d.useragents = append(d.useragents, ua)
+	}
+}
+
 // WithDefaultDialOptions returns an Option that specifies the default
 // DialOptions used.
 func WithDefaultDialOptions(opts ...DialOption) Option {