use admin
var admin = {
    user:"admin",
    pwd:"123456",
    roles:[
        {
            role: "userAdminAnyDatabase",
            db:"admin"
        }
    ]
}
db.createUser(admin)

systemLog:
  destination: file
  path: /Users/me/Web/blog/setup/logs/mongodb/mongo.log
  logAppend: true
storage:
  dbPath: /usr/local/var/mongodb
net:
  port: 27017
  bindIp: 127.0.0.1
security:
  authorization: enabled

mongo 127.0.0.1:27017 --authenticationDatabase admin -u admin -p

MongoDB shell version: 3.2.5
Enter password:
connecting to: 127.0.0.1:27017/test
2018-05-11T08:50:53.908+0300 E QUERY    [thread1] Error: Authentication failed. :
DB.prototype._authOrThrow@src/mongo/shell/db.js:1441:20
@(auth):6:1
@(auth):1:2

exception: login failed