You can go ahead and do the following on your Mac:
GOARCH=riscv GOOS=linux go build
to build a binary that just runs on Linux on RISC-V.These versions are not chosen at random: I ran in to this issue with people trying to run my binary on Ubuntu 16.04 (LTS release), which was solved by linking it statically.
Also, people may use musl libc, and while it has some compatibility with GNU libc this is far from complete.
So in short, linking it statically means it will work for the largest amount of people with a minimal of fuss for both the person building the binaries, and the people running them.
As people have mentioned, these issues are less present on non-Linux systems.
You could also have linked against glibc 2.23 or 2.22 or older instead of bloating your binary.
Adding an extra megabyte or so is a reasonable trade-off, with no real other downsides. It's not that large – smaller than many websites.