GenerateAuthToken function in token model

src/models/token.js

     return user
 }
 
+tokenSchema.statics.generateAuthToken = async function(userArg) {
+    const user = userArg
+    const token = jwt.sign({ _id: user._id.toString() }, 'ovoJeSecret')
+    user.tokens = user.tokens.concat({ token })
+    await user.save()
+
+    return token
+}
+
 const Token = mongoose.model('Token', tokenSchema)
 
 module.exports = Token

src/routers/token.js

         return res.status(400).send('Password is incorrect!')
     }
 
-    const token = await findUser.generateAuthToken()
+    const token = await Token.generateAuthToken(findUser)
 
     return res.send(findUser)
 })