fatal error: stack overflow

runtime stack:
runtime.throw({0x48bb40?, 0x22c4580?})
	GOROOT/src/runtime/panic.go:1047 +0x5d fp=0x7f9f26ffd098 sp=0x7f9f26ffd068 pc=0x10fb0fd
runtime.newstack()
	GOROOT/src/runtime/stack.go:1103 +0x5cc fp=0x7f9f26ffd250 sp=0x7f9f26ffd098 pc=0x11171cc
runtime.morestack()
	src/runtime/asm_amd64.s:570 +0x8b fp=0x7f9f26ffd258 sp=0x7f9f26ffd250 pc=0x112fc6b