Example for Gitea login

steps

• run your gitea on http://localhost:3000
• go to your settings and add an oauth2 application
• change ClientID and ClientSecret on the main.go
• go build and run the program
• visit http://localhost:8000 on your webbrowser, first time you should be prompt to confirm the authorize
• and then you can redirect to your http://localhost:8000 and you can see your user name and email on your gitea instance.