Show HN: I wrote a book about Go(practical-go-lessons.com)

  type Cart interface {
      GetById(ID string) (*cart.Cart, error)
      Put(cart *cart.Cart) (*cart.Cart, error)
  }

  // A type that implements the interface :

  type CartStore struct{}

  func (c *CartStore) GetById(ID string) (*cart.Cart, error) {
      // implement me
  }

  func (c *CartStore) Put(cart *cart.Cart) (\*cart.Cart, error){
      // implement me
  }

    Create a command line application that accepts users inputs as below:

        a. Mandatory "-firstName" flag to accept first name
        b. Mandatory "-lastName" flag to accept last name
        c. Optional "-middleName" flag to accept middle name
        d. Mandatory "-age" flag to accept age - only integers between 0 and 200 should be accepted
        e. Optional "-party" flag to accept political party following - only valid values are "D", "R" and "I"
        d. Optional "-userId" flag to specify user id - if HOME environment variable is set, extract user id from home directory path