As the title says, I wonder if it is possible to change the GC policy used by the Go?
Not in the sense that you can use entirely different collectors like in Java or so on. This is on purpose; they want to get something that works decently well everywhere and avoid GC parameter tuning becoming a specialty for Go programmers.
The most often used option is GOGC. The default value of 100 essentially lets your program grow to twice the amount of live data it had after the last GC before another collection is triggered. 200 would let the program grow to 3x the live data after last GC, 50 would let it grow to only 1.5x. The exact timing and pacing of the collection is a little more complicated under the hood since 1.5 made GC concurrent, but the idea is still to target peak memory use of ~2x the amount of live data.
Practically speaking, the main use of GOGC I've seen is people increasing it to reduce a program's garbage collection workload when they know they have memory to spare. People have run the Go compiler with GOGC=400 or such for a little speedup, for instance. But note it's far more disastrous to bog down your servers by eating a lot of RAM than to spend a few percent more CPU time GC'ing, so don't go overboard with this.
The other knobs that exist are documented in package runtime. With the current implementation you can force GC's to be stop-the-world again or explicitly trigger potentially-stop-the-world collections with runtime.GC(). Separate from GC knobs, runtime also lets you ReadMemStats and get profiles, which are often useful.
You generally don't want to focus much on the little GC tuning possible; defaults work pretty well and your time is usually better spent thinking about your application.