Add go module support

[saschagrunert]

This PR adds a go.mod with the latest dependencies. It would be awesome if we could tag a semver release after this PR got merged, WDYT? :innocent:

[stevvooe]

Is there a way I can verify this is correct? With vendoring, I could check that the code was correct.

To be honest, I don't see any good reason to start having semver releases. We are keeping API stability and I don't want to have more maintenance overhead.

[saschagrunert]

Is there a way I can verify this is correct? With vendoring, I could check that the code was correct.

Yes, it can be checked with something like:

export GO111MODULE=on \
    go mod tidy && \
    go mod vendor && \
    go mod verify

To be honest, I don't see any good reason to start having semver releases. We are keeping API stability and I don't want to have more maintenance overhead.

Alright, sounds good to me too.

[stevvooe]

@saschagrunert I hope you can understand my curmudgeonly position. We can probably do a semver release, if that make things easier. ;)

I did the verify but got a few diffs:

index 5681326..697ea58 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@ go 1.12
 require (
        github.com/gogo/protobuf v1.2.1
        github.com/pkg/errors v0.8.1
+       github.com/prometheus/procfs v0.0.0-20190522114515-bc1a522cf7b1
        github.com/sirupsen/logrus v1.4.1
        golang.org/x/sys v0.0.0-20190514135907-3a4b5fb9f71f
        google.golang.org/genproto v0.0.0-20190513181449-d00d292a067c
diff --git a/go.sum b/go.sum
index 38c5fd0..3716ad0 100644
--- a/go.sum
+++ b/go.sum
@@ -1,6 +1,7 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/gogo/protobuf v1.2.1 h1:/s5zKNz0uPFCZ5hddgPdo2TK2TVrUNMn0OOX8/aZMTE=
 github.com/gogo/protobuf v1.2.1/go.mod h1:hp+jE20tsWTFYpLwKvXlhS1hjn+gTNwPg2I6zVXpSg4=
@@ -11,13 +12,18 @@ github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/kisielk/errcheck v1.1.0/go.mod h1:EZBBE59ingxPouuu3KfxchcWSUPOHkagtvWXihfKN4Q=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+github.com/konsorten/go-windows-terminal-sequences v1.0.1 h1:mweAR1A6xJ3oS2pRaGiHgQ4OO8tzTaLawm8vnODuwDk=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/procfs v0.0.0-20190522114515-bc1a522cf7b1 h1:Lo6mRUjdS99f3zxYOUalftWHUoOGaDRqFk1+j0Q57/I=
+github.com/prometheus/procfs v0.0.0-20190522114515-bc1a522cf7b1/go.mod h1:TjEm7ze935MbeOT/UhFTIMYKhuLP4wbCsTZCD3I8kEA=
 github.com/sirupsen/logrus v1.4.1 h1:GL2rEmy6nsikmW0r8opw9JIRScdMF5hA8cOYLH7In1k=
 github.com/sirupsen/logrus v1.4.1/go.mod h1:ni0Sbl8bgC9z8RoU9G6nDWqqs/fq4eDPysMBDgk/93Q=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -31,6 +37,7 @@ golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=```

I'm not quite sure I understand the reasoning behind that. I am going to upgrade Go (I'm on 1.12.1), so I'll see if that helps.

[saschagrunert]

Yeah no worries, :) having a release tag would be awesome for go module version discovery. In the end it just looks cleaner. I think there went something wrong during my modfile generation, so I decided to regenerate it and added a script to travis which checks for the correctness. WDYT?

[stevvooe]

LGTM

@saschagrunert Thanks!

[dmcgowan]

Is the verify dependencies script meant to replace/fix what is done earlier by go get -t ./...?

[saschagrunert]

Is the verify dependencies script meant to replace/fix what is done earlier by go get -t ./...?

Hm, no its more about consistency checking the contents of the vendor folder.

[estesp]

Now that script/validate/vendor in containerd/project supports go.mod can this PR be updated to use that rather than creating a new script here?

[saschagrunert]

Now that script/validate/vendor in containerd/project supports go.mod can this PR be updated to use that rather than creating a new script here?

Sure, I changed it as suggested.