to go back to 32 bit hardware, you will be running very old machines that you can buy off ebay for <200$ and the power cost offset the new hardware cost in several months.
This sounds like precisely the use-case for x32: Running userland programs that only use 32-bit pointers on x86-64 bit hardware in 64-bit mode; you only get to address 4GB of RAM, but your pointers fit two to a register and you have all the x86-64 registers, opcodes, and special hardware.
This is what I thought. Go is primarily targeted at server-side applications, which are almost exclusively running on 64bit hardware/OS. Memory is so cheap now that it's silly not to have more than 16GB plugged in the chasis.
Then I realized there are many small VPS/EC2 instances with <1GB memory (I have two right now running on 64bit) and there are people who try to squeeze every last bit out of them by going 32bit...
I addition to arm and 32bit OSs, you're going to run into a lot of 32 bit hardware if you try to distribute a program written in Go to the masses (or at all really). I'm using some now.