fatal error: unknown caller pc
D1220 22:16:41.150491       1 task_signals.go:203] [   1:   1] Restarting syscall 202: interrupted by signal 17
D1220 22:16:41.150520       1 task_signals.go:251] [   1:   1] Signal 17: delivering to handler

runtime stack:
runtime.throw(0x14255fe, 0x11)
	GOROOT/src/runtime/panic.go:1117 +0x72 fp=0xc0008dfc30 sp=0xc0008dfc00 pc=0x438072
runtime.gentraceback(0x435cbb, 0xc000a95b58, 0x0, 0xc0006f3b00, 0x0, 0x0, 0x7fffffff, 0xc0008dffa8, 0x0, 0x0, ...)
	GOROOT/src/runtime/traceback.go:261 +0x1a56 fp=0xc0008dff50 sp=0xc0008dfc30 pc=0x460a96
runtime.addOneOpenDeferFrame.func1()
	GOROOT/src/runtime/panic.go:717 +0x91 fp=0xc0008dffd0 sp=0xc0008dff50 pc=0x4695d1
runtime.systemstack(0x0)
	src/runtime/asm_amd64.s:379 +0x66 fp=0xc0008dffd8 sp=0xc0008dffd0 pc=0x470be6
runtime.mstart()
	GOROOT/src/runtime/proc.go:1246 fp=0xc0008dffe0 sp=0xc0008dffd8 pc=0x43d340