Can you explain the working principle of the OAuth protocol and its main features?

OAuth is an authorization protocol that allows third-party applications to obtain limited access to a user's resources without transmitting their password.

Main features of OAuth:

• Uses access tokens instead of passwords.
• Allows the user to control what permissions the application receives.
• Supports various authorization flows (authorization code, implicit, client credentials, etc.).

Working principle:

1. The user initiates authorization through the client application.
2. The client redirects the user to the authorization server.
3. The user authenticates and gives consent.
4. The authorization server issues an access token to the client.
5. The client uses the token to access protected resources.

Example of a simplified flow using the authorization code:

// Pseudocode for obtaining a token
resp, err := http.PostForm("https://auth.server.com/token", url.Values{
    "grant_type": {"authorization_code"},
    "code": {authCode},
    "redirect_uri": {redirectURI},
    "client_id": {clientID},
    "client_secret": {clientSecret},
})
// Then use the obtained token for API requests