Add initial go.mod file

The go.mod file was generated with the following sequence of commands:

go mod init
go mod tidy

The first try resulted in two problems.

- One problem was fixed by updating the import path of nats-server to
  use semantic import v2 in transport/nats/subscriber_test.go.
- The other problem was fixed by changing the required version of
  go.etcd.io/etcd to v0.0.0-20191023171146-3cf2f69b5738 which
  corresponds to v3.4.3. We cannot use the v3.4.3 tag directly because
  of problems within the etcd repo itself described in
  etcd-io/etcd#11154

After those two changes a second go mod tidy succeeds and produces the
go.mod file included in this commit.

go.mod

@@ -0,0 +1,67 @@
+module github.com/go-kit/kit
+
+go 1.13
+
+require (
+	github.com/VividCortex/gohistogram v1.0.0
+	github.com/afex/hystrix-go v0.0.0-20180502004556-fa1af6a1f4f5
+	github.com/apache/thrift v0.13.0
+	github.com/aryann/difflib v0.0.0-20170710044230-e206f873d14a
+	github.com/aws/aws-lambda-go v1.13.3
+	github.com/aws/aws-sdk-go v1.27.0
+	github.com/aws/aws-sdk-go-v2 v0.18.0
+	github.com/casbin/casbin v1.9.1
+	github.com/cenkalti/backoff v2.2.1+incompatible // indirect
+	github.com/clbanning/x2j v0.0.0-20191024224557-825249438eec // indirect
+	github.com/codahale/hdrhistogram v0.0.0-20161010025455-3a0bb77429bd // indirect
+	github.com/coreos/go-semver v0.3.0 // indirect
+	github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f // indirect
+	github.com/davecgh/go-spew v1.1.1
+	github.com/dgrijalva/jwt-go v3.2.0+incompatible
+	github.com/edsrzf/mmap-go v1.0.0 // indirect
+	github.com/franela/goblin v0.0.0-20200105215937-c9ffbefa60db // indirect
+	github.com/franela/goreq v0.0.0-20171204163338-bcd34c9993f8 // indirect
+	github.com/go-logfmt/logfmt v0.5.0
+	github.com/go-stack/stack v1.8.0
+	github.com/golang/protobuf v1.3.2
+	github.com/gorilla/mux v1.7.3
+	github.com/gorilla/websocket v1.4.1 // indirect
+	github.com/grpc-ecosystem/go-grpc-middleware v1.1.0 // indirect
+	github.com/grpc-ecosystem/grpc-gateway v1.12.1 // indirect
+	github.com/hashicorp/consul/api v1.3.0
+	github.com/hashicorp/go-version v1.2.0 // indirect
+	github.com/hudl/fargo v1.3.0
+	github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d
+	github.com/lightstep/lightstep-tracer-go v0.18.1
+	github.com/nats-io/nats-server/v2 v2.1.2
+	github.com/nats-io/nats.go v1.9.1
+	github.com/oklog/oklog v0.3.2
+	github.com/oklog/run v1.0.0 // indirect
+	github.com/op/go-logging v0.0.0-20160315200505-970db520ece7 // indirect
+	github.com/opentracing/basictracer-go v1.0.0 // indirect
+	github.com/opentracing/opentracing-go v1.1.0
+	github.com/openzipkin-contrib/zipkin-go-opentracing v0.4.5
+	github.com/openzipkin/zipkin-go v0.2.2
+	github.com/pact-foundation/pact-go v1.0.4
+	github.com/pborman/uuid v1.2.0
+	github.com/performancecopilot/speed v3.0.0+incompatible
+	github.com/pkg/errors v0.8.1
+	github.com/prometheus/client_golang v1.3.0
+	github.com/samuel/go-zookeeper v0.0.0-20190923202752-2cc03de413da
+	github.com/sirupsen/logrus v1.4.2
+	github.com/smartystreets/goconvey v1.6.4 // indirect
+	github.com/sony/gobreaker v0.4.1
+	github.com/streadway/amqp v0.0.0-20190827072141-edfb9018d271
+	github.com/streadway/handy v0.0.0-20190108123426-d5acb3125c2a
+	github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 // indirect
+	go.etcd.io/etcd v0.0.0-20191023171146-3cf2f69b5738
+	go.opencensus.io v0.22.2
+	go.uber.org/zap v1.13.0
+	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e
+	golang.org/x/time v0.0.0-20191024005414-555d28b269f0
+	golang.org/x/tools v0.0.0-20200103221440-774c71fcf114
+	google.golang.org/grpc v1.26.0
+	gopkg.in/gcfg.v1 v1.2.3 // indirect
+	gopkg.in/warnings.v0 v0.1.2 // indirect
+	sourcegraph.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0
+)