从zip解组特定的XML文件而不解压缩

Question

I have a zip file having several xml files in it using zip and encoding/xml packages from Go archive. The thing I want to do is unmarshalling only a.xml into a type -i.e. without looping over all files inside:

test.zip
├ a.xml
├ b.xml
└ ...

a.xml would have a structure like:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <app>
        <code>0001</code>
        <name>Some Test App</name>
    </app>
    <app>
        <code>0002</code>
        <name>Another Test App</name>
    </app>
</root>

How to for select and unmarshal the file whose name is provided as a parameter in the commented out lines, for instance:

package marshalutils

import (
    "archive/zip"
    "log"
    "fmt"
    "encoding/xml"
)

type ApplicationRoot struct {
    XMLName xml.Name `xml:"root"`
    Applications []Application `xml:"app"`
}

type Application struct {
    Code string `xml:"code"`
    Name string `xml:"name"`
}

func UnmarshalApps(zipPath string, fileName string) {
    // Open a zip archive for reading.
    reader, err := zip.OpenReader(zipFilePath)
    if err != nil {
        log.Fatal(`ERROR:`, err)
    }

    defer reader.Close()

    /* 
     * U N M A R S H A L   T H E   G I V E N   F I L E ...
     * ... I N T O   T H E   T Y P E S   A B O V E
     */
}

Answer 1

Well, here is the answer I have found with the return type declaration added to the sample function:

func UnmarshalApps(zipPath string, fileName string) ApplicationRoot {
    // Open a zip archive for reading.
    reader, err := zip.OpenReader(zipFilePath)
    if err != nil {
        log.Fatal(`ERROR:`, err)
    }

    defer reader.Close()

    /* 
     * START OF ANSWER
     */
    var appRoot ApplicationRoot
    for _, file := range reader.File {
        // check if the file matches the name for application portfolio xml
        if file.Name == fileName {
            rc, err := file.Open()
            if err != nil {
                log.Fatal(`ERROR:`, err)
            }

            // Prepare buffer
            buf := new(bytes.Buffer)
            buf.ReadFrom(rc)

            // Unmarshal bytes
            xml.Unmarshal(buf.Bytes(), &appRoot)
            rc.Close()
        }
    }   
     /* 
     * END OF ANSWER
     */     
}