fixed typos, added error prefix and added usage to README.md

README.md

@@ -1 +1,61 @@
-# jwt - a simple JSON Web Token library in Go
+# jwt - a simple JSON Web Token library written in Go
+
+## Usage
+
+```
+package main
+
+import (
+	"fmt"
+	"git.giftfish.de/ston1th/jwt"
+	"log"
+	"time"
+)
+
+func main() {
+	// create a new signing instance
+	JWT, err := jwt.New(time.Hour, jwt.NewMemBlacklist(), nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// create a new token
+	t := jwt.NewToken(jwt.Claims{
+		"username": "admin",
+	}, nil)
+
+	// sign the token
+	err = JWT.Sign(t)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// print the token string
+	token := t.String()
+	fmt.Println(token)
+
+	// decode the token string
+	newToken, err := jwt.DecodeToken(token)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// verify the decoded token
+	err = JWT.Verify(newToken)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// add the token to the blacklist
+	err = JWT.Invalidate(newToken)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// try to verify the blacklisted token, it should fail
+	err = JWT.Verify(newToken)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+```