2 Docker build issues with easy fix

[johnoloughlin]

Issue 1

 ---> Running in c019ea76f5d2
go: downloading github.com/mattn/go-runewidth v0.0.9
go: downloading github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1
go: finding golang.org/x/net v0.7.0
go: extracting github.com/mattn/go-runewidth v0.0.9
go: downloading golang.org/x/net v0.7.0
go: extracting github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1
go: extracting golang.org/x/net v0.7.0
go: downloading golang.org/x/sys v0.5.0
go: extracting golang.org/x/sys v0.5.0
go: finding github.com/mattn/go-runewidth v0.0.9
go: finding github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1
go: finding golang.org/x/sys v0.5.0
# golang.org/x/sys/unix
/go/pkg/mod/golang.org/x/sys@v0.5.0/unix/syscall.go:83:16: undefined: unsafe.Slice
/go/pkg/mod/golang.org/x/sys@v0.5.0/unix/syscall_linux.go:2271:9: undefined: unsafe.Slice
/go/pkg/mod/golang.org/x/sys@v0.5.0/unix/syscall_unix.go:118:7: undefined: unsafe.Slice
/go/pkg/mod/golang.org/x/sys@v0.5.0/unix/sysvshm_unix.go:33:7: undefined: unsafe.Slice
note: module requires Go 1.17

Issue 2

Step 4/4 : RUN mkdir /out &&     go build .
 ---> Running in 6298105a919c
go: downloading github.com/mattn/go-runewidth v0.0.9
go: downloading github.com/nsf/termbox-go v0.0.0-20200418040025-38ba6e5628f1
client.go:36:2: no required module provides package golang.org/x/net/icmp; to add it:
        go get golang.org/x/net/icmp
client.go:37:2: no required module provides package golang.org/x/net/ipv4; to add it:
        go get golang.org/x/net/ipv4
client.go:38:2: no required module provides package golang.org/x/net/ipv6; to add it:
        go get golang.org/x/net/ipv6

To fix the 2 issues

diff --git a/Dockerfile b/Dockerfile
index 8676acb..936ca02 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,8 +1,10 @@
-FROM golang:1.13
+FROM golang:1.19

 WORKDIR /app

 ADD ./ /app

+RUN go get golang.org/x/net
+
 RUN mkdir /out && \
     go build .
diff --git a/go.mod b/go.mod
index dc863c7..62c1c5e 100644
--- a/go.mod
+++ b/go.mod