fatal error: stack overflow

runtime stack:
runtime.throw({0x123e3a0?, 0x20?})
	GOROOT/src/runtime/panic.go:1077 +0x5c fp=0xc00018de18 sp=0xc00018dde8 pc=0x43ab7c
runtime.newstack()
	GOROOT/src/runtime/stack.go:1107 +0x5ac fp=0xc00018dfc8 sp=0xc00018de18 pc=0x4554cc
runtime.morestack()
	src/runtime/asm_amd64.s:593 +0x8f fp=0xc00018dfd0 sp=0xc00018dfc8 pc=0x46f54f