The warnings / errors you are seeing are coming from the gopls diagnostics feature. There is currently no way to disable the go mod tidy diagnostics. Leaving this open as a feature request.

I think the correct path forward here is probably to allow disabling gopls' modfile diagnostics (or at least control verbosity) rather than to have syntax in the modfile that is only used by gopls.

Generally we try to avoid any changes to the source that exist only to integrate with a single tool.

Ignoring specific warnings would be really nice.

+1 would appreciate a way to disable mod tidy. Or a way to specify -compat=... via env var.

We currently patch this behaviour out of gopls (poorly) and would appreciate a first-class way to completely disable all modfile diagnostics. External tools manage our go.mod / go.sum and vendor tree - we need gopls to trust them and stay away. Large corporate monorepo setting.

+1 would appreciate a way to disable mod tidy. Or a way to specify -compat=... via env var.

Add this function in my ~/.zshrc, ~/.bashrc and /etc/bashrc.. etc
It works in my MBP

function go {
    if [[ $1 == "mod" && $2 == "tidy" ]]; then
        command go mod tidy -compat=1.17 "${@:3}"
    else
        command go "$@"
    fi
}

Despite gopls still throwing errors automatically, there are no issues in terms of usability(gopls formatting and importting works now).