fatal error: unknown caller pc runtime stack: runtime.throw(0x131c5ba, 0x11) GOROOT/src/runtime/panic.go:1117 +0x72 fp=0xc0009a7c30 sp=0xc0009a7c00 pc=0x438072 runtime.gentraceback(0x435cbb, 0xc000213d98, 0x0, 0xc000508780, 0x0, 0x0, 0x7fffffff, 0xc0009a7fa8, 0x0, 0x0, ...) GOROOT/src/runtime/traceback.go:261 +0x1a56 fp=0xc0009a7f50 sp=0xc0009a7c30 pc=0x460a96 runtime.addOneOpenDeferFrame.func1() GOROOT/src/runtime/panic.go:717 +0x91 fp=0xc0009a7fd0 sp=0xc0009a7f50 pc=0x4695d1 runtime.systemstack(0x0) src/runtime/asm_amd64.s:379 +0x66 fp=0xc0009a7fd8 sp=0xc0009a7fd0 pc=0x470be6 runtime.mstart() GOROOT/src/runtime/proc.go:1246 fp=0xc0009a7fe0 sp=0xc0009a7fd8 pc=0x43d340