go env              # Saare Go environment variables
go env GOPATH       # Specific variable
go env GOPROXY GOMODCACHE  # Multiple variables
 
# JSON output
go env -json
 
# Permanently set karo (~/.config/go/env mein)
go env -w GOPROXY=https://goproxy.cn,direct
go env -w GOPRIVATE=*.mycompany.com
 
# Undo (delete from persistent config)
go env -u GOPROXY

# Default: $HOME/go (Linux/Mac), %USERPROFILE%\go (Windows)
GOPATH=/Users/ashutosh/go
 
# Structure:
$GOPATH/
├── bin/        ← go install se binaries
├── pkg/
│   └── mod/   ← module cache
└── src/       ← legacy GOPATH mode code

# Current system
go env GOOS    # darwin / linux / windows
go env GOARCH  # amd64 / arm64 / 386
 
# Cross compile
GOOS=linux GOARCH=amd64 go build .
GOOS=windows GOARCH=386 go build .
 
# ARM (Raspberry Pi)
GOOS=linux GOARCH=arm GOARM=7 go build .

# CGO off karo (pure Go binary, no C dependencies)
CGO_ENABLED=0 go build .
 
# Kab zaroori hai:
# → Static binary banana (no .so dependencies)
# → Alpine Linux containers
# → Cross compilation
# → Docker mein FROM scratch

# Dockerfile example
FROM golang:1.22 AS builder
WORKDIR /app
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -o app .
 
FROM scratch        # minimal base
COPY --from=builder /app/app /app
ENTRYPOINT ["/app"]

# Har go command pe -mod=vendor apply karo
GOFLAGS=-mod=vendor
 
# Multiple flags
GOFLAGS="-mod=vendor -trimpath"
 
# Read-write cache (testing ke liye)
go env -w GOFLAGS=-modcacherw

# Auto (go.mod ki requirements ke anusaar)
GOTOOLCHAIN=auto   # default
 
# Current toolchain ke saath hi chalao
GOTOOLCHAIN=local
 
# Specific version force karo
GOTOOLCHAIN=go1.22.3
 
# Auto but minimum version
GOTOOLCHAIN=auto+go1.21.0

# Workspace off karo (single module mode)
GOWORK=off go build .
 
# Specific go.work file
GOWORK=/path/to/go.work go build .
 
# Auto-detect (default)
GOWORK=""  # parent directories mein dhundo

# Glob patterns (path.Match syntax)
GOPRIVATE=*.corp.example.com,github.com/mycompany/*
 
# Ek baar set karo
go env -w GOPRIVATE=*.mycompany.com
 
# Multiple patterns
go env -w GOPRIVATE="*.corp.example.com,github.com/internal/*"

# Specific modules ke liye HTTP allow karo
GOINSECURE=*.internal.company.org,10.0.0.*
 
# Note: Checksum validation still hota hai
# Checksum skip ke liye GONOSUMDB use karo

# ~/.config/go/env (ya go env -w se set)
GOPRIVATE=*.mycompany.com
GOPROXY=https://goproxy.corp.com,https://proxy.golang.org,direct
GONOSUMDB=*.mycompany.com

# .env ya CI variables mein:
GOPROXY=https://proxy.golang.org,direct
GONOSUMDB=*.internal.com
GOFLAGS=-mod=readonly    # go.mod change nahi hona chahiye CI mein
CGO_ENABLED=0
GOOS=linux
GOARCH=amd64

go env -w GOPROXY=https://goproxy.cn,https://goproxy.io,direct
go env -w GOSUMDB=sum.golang.google.cn

GOPROXY=file:///path/to/module/cache,off
GONOSUMDB=*
GOFLAGS=-mod=vendor

# Dockerfile ARG se pass karo
ARG GOPROXY=https://proxy.golang.org,direct
ARG GONOSUMDB=*.internal.corp
 
RUN --mount=type=cache,target=/go/pkg/mod \
    GOPROXY=${GOPROXY} \
    GONOSUMDB=${GONOSUMDB} \
    CGO_ENABLED=0 \
    go build -o /app ./cmd/server

# Binary mein embed build info dekho
go version -m ./bin/myapp
 
# Output:
./bin/myapp: go1.22.0
        path    github.com/user/myapp/cmd/server
        mod     github.com/user/myapp  v1.2.3  h1:abc...
        dep     github.com/gin-gonic/gin  v1.9.1  h1:xyz...
        dep     go.uber.org/zap  v1.26.0  h1:def...
        build   -buildmode=exe
        build   -compiler=gc
        build   CGO_ENABLED=0
        build   GOARCH=amd64
        build   GOOS=linux

import "runtime/debug"
 
func getBuildInfo() string {
    info, ok := debug.ReadBuildInfo()
    if !ok {
        return "unknown"
    }
    return info.Main.Version
}

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/ashutosh/Library/Caches/go-build"
GOENV="/Users/ashutosh/Library/Application Support/go/env"
GOFLAGS=""
GOINSECURE=""
GOMODCACHE="/Users/ashutosh/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/ashutosh/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTOOLCHAIN="auto"
GOTMPDIR=""
GOWORK=""

# ====== Setup ======
go env -w GOPROXY=https://proxy.golang.org,direct
go env -w GOPRIVATE=*.mycompany.com
go env -w GOPATH=$HOME/go
 
# ====== Cross Compile ======
GOOS=linux GOARCH=amd64 go build -o app-linux .
GOOS=darwin GOARCH=arm64 go build -o app-mac .
GOOS=windows go build -o app.exe .
 
# ====== Static Binary ======
CGO_ENABLED=0 go build -o app .
 
# ====== Debug ======
go env GOPROXY
go env GOMODCACHE
go env GOROOT
 
# ====== Reset ======
go env -u GOPROXY  # Specific variable reset