Move a file to a different drive with Go

You need to make sure that you handle all cases on both Linux and Windows. For example, for any size file,

package main

import (
    "flag"
    "fmt"
    "io"
    "os"
)

func MoveFile(source, destination string) (err error) {
    src, err := os.Open(source)
    if err != nil {
        return err
    }
    defer src.Close()
    fi, err := src.Stat()
    if err != nil {
        return err
    }
    flag := os.O_WRONLY | os.O_CREATE | os.O_TRUNC
    perm := fi.Mode() & os.ModePerm
    dst, err := os.OpenFile(destination, flag, perm)
    if err != nil {
        return err
    }
    defer dst.Close()
    _, err = io.Copy(dst, src)
    if err != nil {
        dst.Close()
        os.Remove(destination)
        return err
    }
    err = dst.Close()
    if err != nil {
        return err
    }
    err = src.Close()
    if err != nil {
        return err
    }
    err = os.Remove(source)
    if err != nil {
        return err
    }
    return nil
}

func main() {
    var src, dst string
    flag.StringVar(&src, "src", "", "source file")
    flag.StringVar(&dst, "dst", "", "destination file")
    flag.Parse()
    if src == "" || dst == "" {
        flag.Usage()
        os.Exit(1)
    }

    err := MoveFile(src, dst)
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        os.Exit(1)
    }
    fmt.Printf("moved %q to %q\n", src, dst)
}

Output (Linux):

$ cp move.file src.file && go build movefile.go && ./movefile -src=src.file -dst=dst.file
moved "src.file" to "dst.file"
$

Output (Windows):

>copy /Y move.file src.file && go build movefile.go && movefile -src=src.file -dst=dst.file
moved "src.file" to "dst.file"
>

As the comment said, you'll need to create a new file on the other disk, copy the contents, and then remove the original. It's straightforward using os.Create, io.Copy, and os.Remove:

import (
    "fmt"
    "io"
    "os"
)

func MoveFile(sourcePath, destPath string) error {
    inputFile, err := os.Open(sourcePath)
    if err != nil {
        return fmt.Errorf("Couldn't open source file: %s", err)
    }
    outputFile, err := os.Create(destPath)
    if err != nil {
        inputFile.Close()
        return fmt.Errorf("Couldn't open dest file: %s", err)
    }
    defer outputFile.Close()
    _, err = io.Copy(outputFile, inputFile)
    inputFile.Close()
    if err != nil {
        return fmt.Errorf("Writing to output file failed: %s", err)
    }
    // The copy was successful, so now delete the original file
    err = os.Remove(sourcePath)
    if err != nil {
        return fmt.Errorf("Failed removing original file: %s", err)
    }
    return nil
}