Adding GOPROXY to Travis (#5018)

* Adding GOPROXY to Travis and fixing libmachine go mod entry

* add comment for weird version

.travis.yml

 language: go
 os: linux
 
+env:
+  - GOPROXY=https://proxy.golang.org
 matrix:
   include:
     - go: 1.12.7

go.mod

@@ -14,7 +14,7 @@ require (
 	github.com/cloudfoundry/jibber_jabber v0.0.0-20151120183258-bcc4c8345a21 // indirect
 	github.com/docker/docker v1.13.1 // indirect
 	github.com/docker/go-units v0.3.3
-	github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5
+	github.com/docker/machine v0.7.1-0.20190718054102-a555e4f7a8f5 // version is 0.7.1 to pin to a555e4f7a8f5
 	github.com/elazarl/goproxy v0.0.0-20190421051319-9d40249d3c2f
 	github.com/elazarl/goproxy/ext v0.0.0-20190421051319-9d40249d3c2f // indirect
 	github.com/go-ole/go-ole v1.2.4 // indirect

go.sum

@@ -106,8 +106,8 @@ github.com/docker/go-connections v0.3.0/go.mod h1:Gbd7IOopHjR8Iph03tsViu4nIes5Xh
 github.com/docker/go-units v0.3.3 h1:Xk8S3Xj5sLGlG5g67hJmYMmUgXv5N4PhkjJHHqrwnTk=
 github.com/docker/go-units v0.3.3/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
 github.com/docker/libnetwork v0.0.0-20180830151422-a9cd636e3789/go.mod h1:93m0aTqz6z+g32wla4l4WxTrdtvBRmVzYRkYvasA5Z8=
-github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5 h1:5OiV/JwT55JRKNJsM9HZrTlJH/TRp97Ee89ahtB78+w=
-github.com/docker/machine v0.16.1-0.20190718054102-a555e4f7a8f5/go.mod h1:I8mPNDeK1uH+JTcUU7X0ZW8KiYz0jyAgNaeSJ1rCfDI=
+github.com/docker/machine v0.7.1-0.20190718054102-a555e4f7a8f5 h1:/2G2PrqxKga8hAVGPri/5NEv24rvDwXoH5pjPXUBCpA=
+github.com/docker/machine v0.7.1-0.20190718054102-a555e4f7a8f5/go.mod h1:I8mPNDeK1uH+JTcUU7X0ZW8KiYz0jyAgNaeSJ1rCfDI=
 github.com/docker/spdystream v0.0.0-20160310174837-449fdfce4d96 h1:cenwrSVm+Z7QLSV/BsnenAOcDXdX4cMv4wP0B/5QbPg=
 github.com/docker/spdystream v0.0.0-20160310174837-449fdfce4d96/go.mod h1:Qh8CwZgvJUkLughtfhJv5dyTYa91l1fOUCrgjqmcifM=
 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=