go mod tidy ipfs library example

[jbouwman]

The code example for using IPFS as a library doesn't run unless indirect dependencies are updated:

$ go version
go version go1.17 linux/amd64
$ uname -a
Linux home 4.19.0-17-amd64 #1 SMP Debian 4.19.194-3 (2021-07-18) x86_64 GNU/Linux
$ go run main.go
go: github.com/ipfs/go-ipfs@v0.9.1 requires
	github.com/ipfs/go-bitswap@v0.4.0: missing go.sum entry; to add it:
	go mod download github.com/ipfs/go-bitswap
go: github.com/ipfs/go-ipfs@v0.9.1 requires
	github.com/ipfs/go-bitswap@v0.4.0: missing go.sum entry; to add it:
	go mod download github.com/ipfs/go-bitswap

Remedied by:

$ go mod tidy
$ go run main.go
-- Getting an IPFS node running --
Spawning node on a temporary repo
    ...

Also, require go version 1.16, otherwise, example can fail under go
1.15 with errors like:

go build github.com/lucas-clemente/quic-go/internal/qtls:
    build constraints exclude all Go files in
    /home/jbouwman/go/pkg/mod/github.com/lucas-clemente/quic-go@v0.23.0/internal/qtls