panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x50a pc=0x4afcf0]

goroutine 44 [running]:
encoding/gob.catchError(0xc000306370)
	/usr/local/go/src/encoding/gob/error.go:38 +0x6d
panic({0xb03320?, 0x12d28d0?})
	/usr/local/go/src/runtime/panic.go:770 +0x132
reflect.Value.FieldByIndex({0xb95040?, 0xc0000eb290?, 0x683b69?}, {0x50a, 0x50a, 0xc0001d1c20?})
	/usr/local/go/src/reflect/value.go:1320 +0x90
encoding/gob.(*Decoder).decodeStruct(0xafc700?, 0xc000301b40, {0xb95040?, 0xc0000eb290?, 0xd9ba80?})
	/usr/local/go/src/encoding/gob/decode.go:489 +0x25c
encoding/gob.(*Decoder).decodeValue(0xc000306300, 0x40, {0xa97ae0?, 0xc0000eb290?, 0xc0007a3d80?})
	/usr/local/go/src/encoding/gob/decode.go:1247 +0x23f
encoding/gob.(*Decoder).DecodeValue(0xc000306300, {0xa97ae0?, 0xc0000eb290?, 0x145be60?})
	/usr/local/go/src/encoding/gob/decoder.go:229 +0x196
encoding/gob.(*Decoder).Decode(0xc000306300, {0xa97ae0?, 0xc0000eb290?})
	/usr/local/go/src/encoding/gob/decoder.go:204 +0x12f
net/rpc.(*gobClientCodec).ReadResponseHeader(0xafb7a0?, 0xa94160?)
	/usr/local/go/src/net/rpc/client.go:228 +0x25
net/rpc.(*Client).input(0xc0000e95c0)
	/usr/local/go/src/net/rpc/client.go:109 +0x9f
created by net/rpc.NewClientWithCodec in goroutine 1
	/usr/local/go/src/net/rpc/client.go:206 +0xb6