diff --git a/README.md b/README.md
index 530f0c7..ef8d703 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 [![coverage-img]][coverage-url]
 [![version-img]][version-url]
 
-OAuth2 client in Go.
+OAuth2 client for Go.
 
 ## Features
 
@@ -40,13 +40,13 @@ client := oauth2.NewClient(http.DefaultClient, config)
 
 // url to fetch the code
 url := client.AuthCodeURL("state")
-fmt.Printf("Visit the URL for the auth dialog: %v", url)
+fmt.Printf("Visit the URL with the auth dialog: %v", url)
 
 // Use the authorization code that is pushed to the redirect URL.
 // Exchange will do the handshake to retrieve the initial access token.
 var code string
 if _, err := fmt.Scan(&code); err != nil {
-    log.Fatal(err)
+    panic(err)
 }
 
 // get a token
@@ -62,6 +62,8 @@ var _ time.Time = token.Expiry    // token expiration time
 var _ bool = token.IsExpired()    // have token expired?
 ```
 
+Also see examples: [example_test.go](https://github.com/cristalhq/oauth2/blob/main/example_test.go).
+
 ## Documentation
 
 See [these docs][pkg-url].
diff --git a/client.go b/client.go
index a1fcdef..094dbd1 100644
--- a/client.go
+++ b/client.go
@@ -10,14 +10,12 @@ import (
 )
 
 // Client represents an OAuth2 HTTP client.
-//
 type Client struct {
 	client *http.Client
 	config Config
 }
 
 // NewClient instantiates a new client with a given config.
-//
 func NewClient(client *http.Client, config Config) *Client {
 	c := &Client{
 		client: client,
@@ -103,7 +101,7 @@ func (c *Client) CredentialsToken(ctx context.Context, username, password string
 // Token renews a token based on previous token.
 func (c *Client) Token(ctx context.Context, refreshToken string) (*Token, error) {
 	if refreshToken == "" {
-		return nil, errors.New("oauth2: refresh token is not set")
+		return nil, errors.New("refresh token is not set")
 	}
 
 	params := url.Values{
@@ -144,10 +142,12 @@ func (c *Client) doRequest(ctx context.Context, mode Mode, params url.Values) (*
 	if err != nil {
 		return nil, err
 	}
+
 	resp, err := c.client.Do(req)
 	if err != nil {
 		return nil, err
 	}
+
 	token, err := parseResponse(resp)
 	if err != nil {
 		return nil, err
diff --git a/go.mod b/go.mod
index 84fc43f..20f6dec 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/cristalhq/oauth2
 
-go 1.17
+go 1.19
diff --git a/token.go b/token.go
index 0ccd690..6478294 100644
--- a/token.go
+++ b/token.go
@@ -9,7 +9,6 @@ import (
 
 // Token represents the credentials used to authorize the requests to access
 // protected resources on the OAuth 2.0 provider's backend.
-//
 type Token struct {
 	AccessToken  string      `json:"access_token"`            // AccessToken is the token that authorizes and authenticates the requests.
 	TokenType    string      `json:"token_type,omitempty"`    // TokenType is the type of token. The Type method returns either this or "Bearer".
@@ -68,7 +67,6 @@ func (t *Token) Extra(key string) interface{} {
 }
 
 // Valid reports whether t is non-nil, has an AccessToken, and is not expired.
-//
 func (t *Token) Valid() bool {
 	return t != nil && t.AccessToken != "" && !t.IsExpired()
 }
@@ -82,7 +80,6 @@ var timeNow = time.Now
 const expiryDelta = 10 * time.Second
 
 // IsExpired reports whether the token is expired.
-//
 func (t *Token) IsExpired() bool {
 	if t.Expiry.IsZero() {
 		return false
diff --git a/wrapper.go b/wrapper.go
index 846fbad..3e89974 100644
--- a/wrapper.go
+++ b/wrapper.go
@@ -7,7 +7,6 @@ import (
 // Wrap adds an additional header to the given http.Client.
 // The header will be `Authorization`.
 // All the params cannot be empty or nil.
-//
 func Wrap(header, value string, c *http.Client) (*http.Client, error) {
 	transport := http.DefaultTransport
 	if c.Transport != nil {