Compiling errors when using the command

HI dear author,  
    It's truly a honor to write a letter to you,  I'm building your project nowadays and found the error when building as following, I wonder if there is a chance that you know the reason? :)

![image](https://user-images.githubusercontent.com/51076736/116841571-309b4800-ac0c-11eb-9810-dd8babd005b7.png)


thank you  
best regards to you  
William  
