本文介紹一款工具 go-callvis，它能夠將 Go 代碼的調用關系可視化出來，并提供了可交互式的 web 服務。

go get -u github.com/ofabry/go-callvis
在windows系統上并沒有自動安裝，需要進入下載的目錄go install
在linux系統上自動安裝了

> go-callvis

go-callvis: visualize call graph of a Go program.

Usage:

? go-callvis [flags] package

? Package should be main package, otherwise -tests flag must be used.

Flags:

? -debug
? ? ? ? Enable verbose log.
? -file string
? ? ? ? output filename - omit to use server mode
? -focus string
? ? ? ? Focus specific package using name or import path. (default "main")
? -format string
? ? ? ? output file format [svg | png | jpg | ...] (default "svg")
? -graphviz
? ? ? ? Use Graphviz's dot program to render images.
? -group string
? ? ? ? Grouping functions by packages and/or types [pkg, type] (separated by comma) (default "pkg")
? -http string
? ? ? ? HTTP service address. (default ":7878")
? -ignore string
? ? ? ? Ignore package paths containing given prefixes (separated by comma)
? -include string
? ? ? ? Include package paths with given prefixes (separated by comma)
? -limit string
? ? ? ? Limit package paths to given prefixes (separated by comma)
? -minlen uint
? ? ? ? Minimum edge length (for wider output). (default 2)
? -nodesep float
? ? ? ? Minimum space between two adjacent nodes in the same rank (for taller output). (default 0.35)
? -nointer
? ? ? ? Omit calls to unexported functions.
? -nostd
? ? ? ? Omit calls to/from packages in standard library.
? -skipbrowser
? ? ? ? Skip opening browser.
? -tags build tags
? ? ? ? a list of build tags to consider satisfied during the build. For more information about build tags, see the description of buil
d constraints in the documentation for the go/build package
? -tests
? ? ? ? Include test code.
? -version
? ? ? ? Show version and exit.

依賴

• Go 1.17+
• Graphviz (可選，當工具指定了 -graphviz 時需要)

測試代碼

package main
import (
	"log"
	"net"
)
func main() {
	// Part 1: create a listener
	l, err := net.Listen("tcp", ":8000")
	if err != nil {
		log.Fatalf("Error listener returned: %s", err)
	}
	defer l.Close()
	for {
		// Part 2: accept new connection
		c, err := l.Accept()
		if err != nil {
			log.Fatalf("Error to accept new connection: %s", err)
		}
		// Part 3: create a goroutine that reads and write back data
		go func() {
			log.Printf("TCP session open")
			defer c.Close()
			for {
				d := make([]byte, 1024)
				// Read from TCP buffer
				_, err := c.Read(d)
				if err != nil {
					log.Printf("Error reading TCP session: %s", err)
					break
				}
				log.Printf("reading data from client: %s\n", string(d))
				// write back data to TCP client
				_, err = c.Write(d)
				if err != nil {
					log.Printf("Error writing TCP session: %s", err)
					break
				}
			}
		}()
	}
}

在linux上可以正常運行，windows上會報錯

> go-callvis main67.go
2022/09/21 15:28:50 http serving at http://localhost:7878

go-callvis 默認將代碼調用關系存儲成 svg 格式的圖形。

在瀏覽器中訪問 http://localhost:7878

點擊上面的 log 模塊，將會進入 log 模塊的代碼調用交互圖中

它主要是作用是清晰的列出了包與包之間的依賴以及調用關系，用來理解項目的大致架構。