Error on execute de api

I'm getting: "System.IO.FileNotFoundException: 'Could not load file or assembly 'RiotGamesApi, Version=1.10.4.10, Culture=neutral, PublicKeyToken=null'. O sistema não pode encontrar o arquivo especificado.'" on use in the dot net core. I'm try with the example error from the tutorial.

Startup.cs: https://pastebin.com/537VmJwN

Thanks.

Sorry for my bad english.