go build -> goptlib.git/go.mod at revision v1.1.0: unknown revision v1.1.0

Hello, on old CentOS 6.10, 2.6.32-042stab145.3 was

Installed: git.x86_64 0:1.7.1-10.el6_10 golang-bin.x86_64 0:1.15.2-1.el6

Dependency Installed: golang.x86_64 0:1.15.2-1.el6 golang-src.noarch 0:1.15.2-1.el6 libproxy.x86_64 0:0.3.0-10.el6 libproxy-bin.x86_64 0:0.3.0-10.el6 libproxy-python.x86_64 0:0.3.0-10.el6 mercurial.x86_64 0:1.4-5.el6_9 neon.x86_64 0:0.29.3-3.el6_4 pakchois.x86_64 0:0.4-3.2.el6 perl-Git.noarch 0:1.7.1-10.el6_10 perl-URI.noarch 0:1.40-2.el6 subversion.x86_64 0:1.6.11-15.el6_7

cd
git clone https://git.torproject.org/pluggable-transports/snowflake.git
cd snowflake/proxy
go build

go: git.torproject.org/pluggable-transports/goptlib.git@v1.1.0: reading git.torproject.org/pluggable-transports/goptlib.git/go.mod at revision v1.1.0: unknown revision v1.1.0

I am wondering if you can please suggest me to try something to workaround this? From https://go.dev/doc/install/source#install i do not understand which commands i need to try in my case.

Or if you can do something on your side? Thank you