Add go.mod to the repository (#502)

* Add go.mod/go.sum

* travis: update to test in modules mode and with go1.13

Remove go1.11 setup

* fix appveyor config

AppVeyor sets the latest go stack in C:\go and that is GOROOT.
Cloning this repo under C:\go\src\.. directory confused go build
(as discussed in golang/go#34657). The fix in go is not yet
released. Thus this commit changes GOPATH to c:\gopath and clones
the repo under the directory.

Also, this commit removes the go get commands intended to pull in
dependencies. In modules mode, `go build` pulls in the required
dependencies.

.travis.yml

 
 matrix:
   include:
-    - os: linux
-      go: 1.11.x
     - os: linux
       go: 1.12.x
+    - os: linux
+      go: 1.13.x
     - os: linux
       go: master
     - os: osx
       osx_image: xcode8.3
-      go: 1.11.x
+      go: 1.12.x
     - os: osx
       osx_image: xcode8.3
-      go: 1.12.x
+      go: 1.13.x
     - os: osx
       osx_image: xcode8.3
       go: master
     - os: osx
       osx_image: xcode9.4
-      go: 1.11.x
+      go: 1.12.x
     - os: osx
       osx_image: xcode9.4
-      go: 1.12.x
+      go: 1.13.x
     - os: osx
       osx_image: xcode9.4
       go: master
     - os: osx
       osx_image: xcode10.1
-      go: 1.11.x
+      go: 1.12.x
     - os: osx
       osx_image: xcode10.1
-      go: 1.12.x
+      go: 1.13.x
     - os: osx
       osx_image: xcode10.1
       go: master
     packages:
       - graphviz
     update: true
-    
+ 
 before_install:
-  - go get -u golang.org/x/lint/golint honnef.co/go/tools/cmd/...
+  # Do not let tools interfere with the main module's go.mod
+  - env GO111MODULE=off go get -u golang.org/x/lint/golint honnef.co/go/tools/cmd/...
 
 script:
   - gofmtdiff=$(gofmt -s -d .) && if [ -n "$gofmtdiff" ]; then printf 'gofmt -s found:\n%s\n' "$gofmtdiff" && exit 1; fi
   - go vet -all ./...
   - ./test.sh
 
+  # Check still works in GOPATH mode.
+  - env GO111MODULE=off go get -d . && go test -v ./...
+
 after_success:
   - bash <(curl -s https://codecov.io/bash)

appveyor.yml

-clone_folder: c:\go\src\github.com\google\pprof
+clone_folder: c:\gopath\src\github.com\google\pprof
+
+environment:
+  GOPATH: c:\gopath
 
 install:
  - cinst graphviz
 
-before_build:
- - go get github.com/ianlancetaylor/demangle
- - go get github.com/chzyer/readline
-
 build_script:
+ - go env
  - go build github.com/google/pprof
 
 test_script:

go.mod

+module github.com/google/pprof
+
+go 1.14
+
+require (
+	github.com/chzyer/logex v1.1.10 // indirect
+	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e
+	github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 // indirect
+	github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6
+	golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e // indirect
+)

go.sum

+github.com/chzyer/logex v1.1.10 h1:Swpa1K6QvQznwJRcfTfQJmTE72DqScAa40E+fbHEXEE=
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e h1:fY5BOSpyZCqRo5OhCuC+XN+r/bBCmeuuJtjz+bCNIf8=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 h1:q763qf9huN11kDQavWsoZXJNW3xEE4JJyHa5Q25/sd8=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
+github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6 h1:UDMh68UUwekSh5iP2OMhRRZJiiBccgV7axzUG8vi56c=
+github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
+golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e h1:9vRrk9YW2BTzLP0VCB9ZDjU4cPqkg+IDWL7XgxA1yxQ=
+golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=