Overview

Package shouchan provides simple configuration management for Golang application, with following features:

• read configuration from command line flag and/or YAML file, mix&match, into a struct
• 3 sources: default value, YAML file and flag
• priority:in case of multiple source returns same config struct field, the preference is flag over YAML over default value

include support following field types:

• integer types
• float type
• string
• time.Duration
• and all types that implement encoding.TextMarshaler and encoding.TextUnmarshaler interface
• there is also github.com/hujun-open/shouchantypes include some other types

Additional types could be supported by using Register, see github.com/hujun-open/shouchantypes for example.

CLI & YAML Support

• YAML: shouchan uses extyaml for YAML marshal and unmarshal
• CLI Flag: shouchan uses myflags for command line flag generation

refer to corresponding doc for details on CLI & YAML support.

Example:

shouchan/example/main.go

Lines 1 to 57 in 809751e

	package main
	import (
	"fmt"
	"net"
	"net/netip"
	"time"
	"github.com/hujun-open/shouchan"
	_ "github.com/hujun-open/shouchantypes"
	)
	type Company struct {
	//the usage tag is used for command line usage
	Name string `usage:"company name"`
	}
	type Employee struct {
	Name string `usage:"employee name"`
	Addr *string `usage:"employee address"`
	Naddr *netip.Addr
	N2addr netip.Addr
	IPAddr net.IP `usage:"employee IP address"`
	Subnet net.IPNet `usage:"employee IP subnet"`
	MAC net.HardwareAddr `usage:"employee MAC address"`
	JointTime time.Time `usage:"employee join time"`
	Employer Company
	}
	func main() {
	//default config
	def := Employee{
	Name: "defName",
	N2addr: netip.AddrFrom4([4]byte{1, 1, 1, 1}),
	IPAddr: net.ParseIP("1.2.3.4"),
	MAC: net.HardwareAddr{0x11, 0x22, 0x33, 0x44, 0x55, 0x66},
	Employer: Company{
	Name: "defCom",
	},
	}
	def.Addr = new(string)
	*def.Addr = "defAddrPointer"
	def.Naddr = new(netip.Addr)
	*def.Naddr = netip.AddrFrom4([4]byte{2, 2, 2, 2})
	_, prefix, _ := net.ParseCIDR("192.168.1.0/24")
	def.Subnet = *prefix
	def.JointTime, _ = time.Parse(time.DateTime, "2023-01-02 13:22:33")
	cnf, err := shouchan.NewSConf(&def, "example", "shouchan example",
	shouchan.WithDefaultConfigFilePath[*Employee]("test.yaml"))
	if err != nil {
	panic(err)
	}
	ferr, aerr := cnf.ReadwithCMDLine()
	fmt.Printf("ferr %v,aerr %v\n", ferr, aerr)
	fmt.Printf("final result is %+v\n", cnf.GetConf())
	}

Output:

• Usage

 .\test.exe -?
flag provided but not defined: -?
shouchan example
  - addr: employee address
        default:defAddrPointer
  - employer-name: company name
        default:defCom
  - ipaddr: employee IP address
        default:1.2.3.4
  - jointtime: employee join time
        default:2023-01-02 13:22:33
  - mac: employee MAC address
        default:11:22:33:44:55:66
  - n2addr:
        default:1.1.1.1
  - naddr:
        default:2.2.2.2
  - name: employee name
        default:defName
  - subnet: employee IP subnet
        default:192.168.1.0/24

  -cfgfromfile: load configuration from the specified file
        default:test.yaml

• no command line args, no config file, default is used

 .\test.exe   
ferr failed to open config file test.yaml, open test.yaml: The system cannot find the file specified.,aerr <nil>
final result is &{Name:defName Addr:0xc0000528b0 Naddr:2.2.2.2 N2addr:1.1.1.1 IPAddr:1.2.3.4 Subnet:{IP:192.168.1.0 Mask:ffffff00} MAC:11:22:33:44:55:66 JointTime:2023-01-02 13:22:33 +0000 UTC Employer:{Name:defCom}}

• config file via "-f" command args, value from file take procedence

 .\test.exe -cfgfromfile cfg.yaml
ferr <nil>,aerr <nil>
final result is &{Name:nameFromFile Addr:0xc0000528b0 Naddr:2.2.2.2 N2addr:1.1.1.1 IPAddr:1.2.3.4 Subnet:{IP:192.168.1.0 Mask:ffffff00} MAC:11:22:33:44:55:66 JointTime:2023-01-02 13:22:33 +0000 UTC Employer:{Name:comFromFile}}

• mix command line args and config file, args to override employee name:

.\test.exe -cfgfromfile cfg.yaml -name nameFromArg
ferr <nil>,aerr <nil>
final result is &{Name:nameFromArg Addr:0xc000088880 Naddr:2.2.2.2 N2addr:1.1.1.1 IPAddr:1.2.3.4 Subnet:{IP:192.168.1.0 Mask:ffffff00} MAC:11:22:33:44:55:66 JointTime:2023-01-02 13:22:33 +0000 UTC Employer:{Name:comFromFile}}

• mix command line args and config file, args to override company name:

.\test.exe -cfgfromfile cfg.yaml -employer-name comFromArg
ferr <nil>,aerr <nil>
final result is &{Name:nameFromFile Addr:0xc000104880 Naddr:2.2.2.2 N2addr:1.1.1.1 IPAddr:1.2.3.4 Subnet:{IP:192.168.1.0 Mask:ffffff00} MAC:11:22:33:44:55:66 JointTime:2023-01-02 13:22:33 +0000 UTC Employer:{Name:comFromArg}}

Code Generation

shouchan also provides a code generation tool to deal with large amount of constants, see shouchangen.