golang mod开发模式

用变量 GO111MODULE 开启或关闭模块支持，它有三个可选值：off、on、auto，默认值是 auto。
GO111MODULE=off 无模块支持，go 会从 GOPATH 和 vendor 文件夹寻找包。
GO111MODULE=on 模块支持，go 会忽略 GOPATH 和 vendor 文件夹，只根据 go.mod 下载依赖。
GO111MODULE=auto 在 $GOPATH/src 外面且根目录有 go.mod 文件时，开启模块支持。
在使用模块的时候，GOPATH 是无意义的，不过它还是会把下载的依赖储存在 $GOPATH/src/mod 中，
也会把 go install 的结果放在 $GOPATH/bin 中。
golang版本为1.14。设置方式为  go env -w GO111MODULE=on

goland中开启go module，设置 https://goproxy.cn,direct
差点忘了go断言的类型转换

package main

import (
    "encoding/json"
    "fmt"
    "github.com/twpayne/go-geom"
    "github.com/twpayne/go-geom/encoding/geojson"
    "github.com/twpayne/go-geom/encoding/wkt"
    "reflect"
)

func main() {
    unitSquare := geom.NewPolygon(geom.XY).MustSetCoords([][]geom.Coord{
        {{0, 0}, {1, 0}, {1, 1}, {0, 2}, {0, 0}},
    })

    fmt.Printf("unitSquare.Area() == %f", unitSquare.Area())
    // geom -> wkt
    unitSquareWkt, _ := wkt.Marshal(unitSquare)
    fmt.Println(unitSquareWkt)

    // wkt -> geom
    if geomFromWkt, err := wkt.Unmarshal("POLYGON ((0 0, 1 0, 1 1, 0 2, 0 0))"); err != nil {
        fmt.Println(err)
    } else {
        if p, ok := geomFromWkt.(*geom.Polygon); ok != true {
            fmt.Println(ok)
        } else {
            coords := p.Coords()
            for i, v := range coords {
                for j, v2 := range v {
                    fmt.Printf("arr[%v][%v]=%v \t \n", i, j, v2)
                }
                fmt.Println()
            }
        }
        fmt.Println(reflect.TypeOf(geomFromWkt).Elem())
    }

    // geom -> geomJson
    bytes, _ := geojson.Marshal(unitSquare)
    fmt.Println(string(bytes))

    // geoJson -> geom
    var geomFromGeojson geom.T;
    a := `{"type":"Polygon","coordinates":[[[0,0],[1,0],[1,1],[0,2],[0,0]]]}`
    if err := geojson.Unmarshal([]byte(a), &geomFromGeojson); err != nil {
        fmt.Println(err)
    } else {
        if p, ok := geomFromGeojson.(*geom.Polygon); ok != true {
            fmt.Println(ok)
        } else {
            coords := p.Coords()
            for i, v := range coords {
                for j, v2 := range v {
                    fmt.Printf("arr[%v][%v]=%v \t \n", i, j, v2)
                }
                fmt.Println()
            }
        }
        fmt.Println(reflect.TypeOf(geomFromGeojson).Elem())
    }

    // feature -> featureJson
    feature := geojson.Feature{}
    feature.Geometry = geomFromGeojson
    properties := make(map[string]interface{})
    properties["prop0"] = "value0"
    properties["prop1"] = "1.2"
    feature.Properties = properties
    featureJson, _ := feature.MarshalJSON()
    fmt.Println(string(featureJson))

    // featureJson -> feature
    var m map[string]interface{}
    json.Unmarshal(featureJson,&m)
    marshal, _ := json.Marshal(m["geometry"])
    fmt.Println(string(marshal))

    // featureCollectionJson
    var features [3]*geojson.Feature
    features[0] = &feature
    features[1] = &feature
    features[2] = &feature
    featureCollecation1 := geojson.FeatureCollection{Features: features[:2]}
    featureCollecationJSON1, _ := featureCollecation1.MarshalJSON()
    fmt.Println(string(featureCollecationJSON1))
    fmt.Println(len(featureCollecation1.Features))

    featureCollecation2 := geojson.FeatureCollection{}
    featureCollecation2.Features = append(featureCollecation2.Features, &feature)
    featureCollecation2.Features = append(featureCollecation2.Features, &feature)
    featureCollecationJSON2, _ := featureCollecation2.MarshalJSON()
    fmt.Println(string(featureCollecationJSON2))
    fmt.Println(len(featureCollecation2.Features))

    point := geom.NewPoint(geom.XY).MustSetCoords(geom.Coord{1.0, 1.0})
    pointWkt, _ := wkt.Marshal(point)
    fmt.Println(pointWkt)
    
    multipoint := geom.NewMultiPoint(geom.XY).MustSetCoords([]geom.Coord{{1.0, 1.0}, {2, 2}})
    multipointWkt, _ := wkt.Marshal(multipoint)
    fmt.Println(multipointWkt)
    
    line := geom.NewLineString(geom.XY).MustSetCoords([]geom.Coord{{1.0, 1.0}, {2, 2}})
    lineWkt, _ := wkt.Marshal(line)
    fmt.Println(lineWkt)
    
    mutiline := geom.NewMultiLineString(geom.XY)
    mutiline.Push(line)
    mutiline.Push(line)
    mutiline.SetSRID(4326)
    mutilineWkt, _ := wkt.Marshal(mutiline)
    fmt.Println(mutilineWkt)
}

有疑问加站长微信联系（非本文作者）