Currently I've found the solution:

Inside the serviceA/go.mod:

module serviceA

replace (
    common v0.0.0 => ../common
)

require (
    common v0.0.0
)

Also, seems like common would not work if it will not look like url, so it must be common.org or something like this (in other way vgo will check $GOROOT dir for such package).

Any way, what is the convenient way to store the v folder in the project repository?

Sorry for missing this when it came in. The top-level domain problem was real and I believe was fixed. It sounds like you got everything working once you added the require statement. I filed #26241 to try to make that experience better.

Any way, what is the convenient way to store the v folder in the project repository?

I'm not sure what you mean by "the v folder". I see it in the tree output, but I don't know what is in it. If it's like common, then the way is to give it an import prefix.

I want to use $GOPATH as a root of git monorepo with several projects sharing some common library:

I think this is the mismatch. Typically instead of making the monorepo hold all of $GOPATH, you should make the root correspond to some directory like "$GOPATH/src/you.com/myrepo". Then "common" would be at the top level of the repo but imported as "you.com/myrepo/common", and similarly the go.mod would say "module you.com/myrepo/common". And then v would be the same: "module you.com/myrepo/v".

Thank you for reply! Will try to use your advice =)