This is the main code for generating the builder design pattern from templates.

codegen_builder.go

package main 

import ( 
    "bufio"
    "bytes" 
    "fmt" 
    "github.com/Masterminds/sprig" 
    "go/format" 
    "html/template" 
    "log"  
    "os" 
) 

type Data struct { 
    ProductTarget   string 
    ConcreteTargets []string 
    Properties      []Property 
} 

type Property struct { 
    Name     string 
    TypeName string 
} 

func main() { 
    data := Data{ 
        ProductTarget:   "house", 
        ConcreteTargets: []string{"normal", "igloo"}, 
        Properties: []Property{ 
            {"windowType", "string"}, 
            {"doorType", "string"}, 
            {"floor", "int"}, 
        }, 
    } 
    processTemplate("iBuilder.tmpl", "iBuilder.go", data) 
    processTemplate("ProductTarget.tmpl", data.ProductTarget+".go", data) 
    processTemplate("director.tmpl", "director.go", data) 
    processTemplate("sample_main.tmpl", "sample_main.go", data) 
    processConcreteTargets("ConcreteTarget.tmpl", data) 
    fmt.Println("Remember to edit the files that contain the Concrete Targets!") 
}
 
func processTemplate(fileName string, outputFile string, data Data) { 
    tmpl := template.Must(template.New("").Funcs(sprig.FuncMap()).ParseFiles(fileName)) 
    var processed bytes.Buffer 
    err := tmpl.ExecuteTemplate(&processed, fileName, data) 
    if err != nil { 
        log.Fatalf("Unable to parse data into template: %v\n", err) 
    } 
    formatted, err := format.Source(processed.Bytes()) 
    if err != nil { 
        log.Fatalf("Could not format processed template: %v\n", err) 
    } 
    outputPath := "./tmp/" + outputFile 
    fmt.Println("Writing file: ", outputPath) 
    f, _ := os.Create(outputPath) 
    w := bufio.NewWriter(f) 
    w.WriteString(string(formatted)) 
    w.Flush() 
} 

func processConcreteTargets(fileName string, data Data) { 
    for _, value := range data.ConcreteTargets { 
        newData := data 
        newData.ConcreteTargets = []string{value} 
        processTemplate(fileName, value+".go", newData) 
    } 
}