Bypassing the error by "go get" "tls: failed to verify certificate: x509: certificate signed by unknown authority"

When I was trying to download dependencies for my go project in an old Ubuntu machine I was getting this error all the time:

"go: gopkg.in/alexcesaro/quotedprintable.v3@v3.0.0-20150716171945-2caba252f4dc: Get "https://proxy.golang.org/gopkg.in/alexcesaro/quotedprintable.v3/@v/v3.0.0-20150716171945-2caba252f4dc.mod": tls: failed to verify certificate: x509: certificate signed by unknown authority"

Which the main part of it was go get failing to authenticate: "tls: failed to verify certificate: x509: certificate signed by unknown authority"

I tried many things but couldn't make it work until I found the way:

export GOINSECURE="proxy.golang.go"

This will tell go get to ignore certification validity.

Then

export GOPROXY=direct

This will tell go get to by pass proxy

Then

git config --global http.sslverify false

And only after those I could run again:

go get

And it worked