Close #85 #112, Go mod round2

[ChihChengLiang]

Note

• For future module update, use make update-go-mod

What was wrong?

• This continued #91, which tries to address #85. The go mod works this time.
• It also addressed #112 by COPYing file to a /bin directory

How was it fixed?

• This command gets the package with the latest commit on master branch go get -v github.com/libp2p/go-libp2p-crypto@master.

Cute Animal Picture

[ChihChengLiang]

@NIC619 This works now, also I think we can remove gx completely.

[ChihChengLiang]

@mhchia @NIC619 The focus of the review is whether the new setup works on your environments.

[ChihChengLiang]

@NIC619 Thanks for reviewing. After some trying, I feel it's better to update README.md after #127.

[ChihChengLiang]

Thank you @mhchia & @NIC619 for reviewing ❤️