[jacobf]

Hello, I have a quick question. I was going through the Core 1000 series on iKnow.jp and I found this example sentence:

上司が「一杯、飲もう」と言った。

The part I am confused about is: 「一杯、飲もう」.
According to the translation on the page, this comes out to be "Let's have a drink." Now, with my very limited knowledge, I think this is roughly "Drink a drink". Is the "Let's have a..." part implied or something? Or is 一杯、飲もう a common way to say "Let's have a drink"?

Thank you for your time.