[code=golang]
import (
    "image"
    _ "image/gif"
    _ "image/jpeg"
    _ "image/png"
    "os"
)

func GetImageSize(filename string) (int, int, error) {
    file, err := os.Open(filename)
    if err != nil {
        return 0, 0, err
    }
    defer file.Close()

    config, _, err := image.DecodeConfig(file)
    if err != nil {
        return 0, 0, err
    }

    return config.Width, config.Height, nil
}

[/code]