如果不设置，直接使用命令创建会报错，如下：
go: modules disabled inside GOPATH/src by GO111MODULE=auto; see 'go help mod
01、配置GO111MODULE=on环境变量：配置后，最好是重启一下电脑，以免没有生效，搞得自己很烦。
02、使用命令：go mod init
03、在go.mod文件中添加require：
04、在项目中执行命令：go mod download，执行后会生成go.sum文件：
D:Gosrcapple> PS D:Gosrcapple> go mod download go: finding gopkg.in/yaml.v2 v2.2.2 go: finding github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c go: finding github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57 go: finding golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2 go: finding golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6 go: finding golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421 go: finding go.opencensus.io v0.20.1 go: finding golang.org/x/exp v0.0.0-20190121172915-509febef88a4 go: finding google.golang.org/grpc v1.19.0 go: finding golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f go: finding golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 go: finding github.com/golang/protobuf v1.2.0 go: finding github.com/googleapis/gax-go/v2 v2.0.4 go: finding github.com/apache/thrift v0.12.0 go: finding github.com/golang/mock v1.2.0 go: finding honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a go: finding cloud.google.com/go v0.34.0 go: finding golang.org/x/net v0.0.0-20180826012351-8a410e7b638d go: finding golang.org/x/net v0.0.0-20190108225652-1e06a53dbb7e go: finding honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099 go: finding github.com/google/martian v2.1.0+incompatible go: finding github.com/google/go-cmp v0.2.0 go: finding github.com/hashicorp/golang-lru v0.5.0 go: finding golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be go: finding golang.org/x/sys v0.0.0-20180830151530-49385e6e1522 go: writing stat cache: rename D:Gopkgmodcachedownloadgolang.orgxsys@vv0.0.0-20180830151530-49385e6e1522.info689223850.tmp
D:Gopkgmodcachedownloadgolang.orgxsys@vv0.0.0-20180830151530-49385e6e1522.info: Access is denied. go: finding github.com/golang/mock v1.1.1 go: finding github.com/openzipkin/zipkin-go v0.1.6 go: finding github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b go: finding cloud.google.com/go v0.26.0 go: finding github.com/client9/misspell v0.3.4 go: finding github.com/prometheus/client_model v0.0.0-20190115171406-56726106282f go: finding google.golang.org/api v0.3.1 go: finding github.com/prometheus/common v0.2.0 go: finding golang.org/x/sync v0.0.0-20181108010431-42b317875d0f go: finding github.com/Shopify/toxiproxy v2.1.4+incompatible go: finding github.com/onsi/ginkgo v1.7.0 go: finding github.com/eapache/go-resiliency v1.1.0 go: finding github.com/prometheus/procfs v0.0.0-20190117184657-bf6a532e95b1 go: finding github.com/onsi/gomega v1.4.3 go: finding github.com/Shopify/sarama v1.19.0 go: finding golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5 go: finding github.com/rcrowley/go-metrics v0.0.0-20181016184325-3113b8401b8a go: finding github.com/matttproud/golang_protobuf_extensions v1.0.1 go: finding github.com/gorilla/context v1.1.1 go: finding github.com/prometheus/procfs v0.0.0-20181005140218-185b4288413d go: finding github.com/pierrec/lz4 v2.0.5+incompatible go: finding golang.org/x/net v0.0.0-20180906233101-161cd47e91fd go: writing go.mod cache: rename D:Gopkgmodcachedownloadgithub.comprometheusprocfs@vv0.0.0-20181005140218-185b4288413d.mod373518781.tmp
D:Gopkgmodcachedownloadgithub.comprometheusprocfs@vv0.0.0-20181005140218-185b4288413d.mod: Access is denied. go: finding github.com/gogo/protobuf v1.1.1 go: finding github.com/fsnotify/fsnotify v1.4.7 go: finding gopkg.in/fsnotify.v1 v1.4.7 go: finding github.com/julienschmidt/httprouter v1.2.0 go: finding github.com/go-logfmt/logfmt v0.3.0 go: finding github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515 go: finding google.golang.org/genproto v0.0.0-20190404172233-64821d5d2107 go: finding github.com/pkg/errors v0.8.0 go: finding golang.org/x/tools v0.0.0-20190226205152-f727befe758c go: finding github.com/sirupsen/logrus v1.2.0 go: finding github.com/go-kit/kit v0.8.0 go: finding github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223 go: finding github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf go: finding github.com/onsi/ginkgo v1.6.0 go: finding github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc go: finding gopkg.in/alecthomas/kingpin.v2 v2.2.6 go: finding golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33 go: finding github.com/stretchr/objx v0.1.1 go: finding github.com/konsorten/go-windows-terminal-sequences v1.0.1 go: finding golang.org/x/crypto v0.0.0-20180904163835-0709b304e793 go: finding github.com/hpcloud/tail v1.0.0 PS D:Gosrcapple> go mod download PS D:Gosrcapple>
05、查看软件包的版本信息：
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