Debugging Invalid Memory Address

I'm building a simple Go application, but when I execute my program on Windows 10, I get this error: Update: The full stacktrace is now included.

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x18 pc=0x478edd]

goroutine 1 [running]:
github.com/UpperCenter/Amalthea/src/files.(*Files).ScanToEncrypt.func1(0xc000162aa0, 0x4c, 0x4caaa0, 0xc000167b20, 0x0, 0x0, 0x4c, 0x2)
        /home/uppercenter/Amalthea/src/files/files.go:48 +0x13d
path/filepath.walk(0xc000162aa0, 0x4c, 0x4caaa0, 0xc000167b20, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:360 +0x443
path/filepath.walk(0xc000560e10, 0x30, 0x4caaa0, 0xc000167500, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.walk(0xc0001719b0, 0x24, 0x4caaa0, 0xc000191650, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.walk(0xc000011720, 0x1a, 0x4caaa0, 0xc000180000, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.walk(0xc0000116a0, 0x14, 0x4caaa0, 0xc000175dc0, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.walk(0xc00000acc0, 0xc, 0x4caaa0, 0xc000174af0, 0xc000221d18, 0x0, 0x0)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.walk(0x4a4206, 0x9, 0x4caaa0, 0xc00010a000, 0xc000221d18, 0x0, 0x457a58)
        /usr/lib/go/src/path/filepath/path.go:384 +0x31a
path/filepath.Walk(0x4a4206, 0x9, 0xc000077d18, 0x280, 0x26c)
        /usr/lib/go/src/path/filepath/path.go:406 +0x10c
github.com/UpperCenter/Amalthea/src/files.(*Files).ScanToEncrypt(0xc000077f48, 0xc000006018, 0xc000077df8, 0x1, 0x1, 0x26c)
        /home/uppercenter/Amalthea/src/files/files.go:40 +0x86
main.main()
        /home/uppercenter/Amalthea/main.go:63 +0x193

I read that this has happened because I have an error within ScanToEncrypt that isn't being handled.

Here's the ScanToEncrypt function:

// ScanToEncrypt scans all valid files to encrypt
func (f *Files) ScanToEncrypt() ([]string, error) {
    // Store encryptable files as array.
    var files []string
    // Begin "walking" from `rootDir` to get all available folders & subfolders
    err := filepath.Walk(f.rootDir, func(path string, info os.FileInfo, err error) error {
        // Returns info describing a named file.
        stat, _ := os.Stat(path)
        // HasSuffix looks for encoded files.
        if !strings.HasSuffix(path, ".AmaltheaEnc") {
            if !stat.IsDir() {
                // Checks the file is below maximum file size in bytes defined by `size`
                if stat.Size() <= int64(f.size) {
                    for _, ext := range f.exts {
                        if strings.Contains(path, "."+ext) {
                            // Append file & file path to `files`
                            files = append(files, path)
                            break
                        }
                    }
                }
            }
        }
        return nil
    })
    // Return `files` array to use for encryption
    return files, err
}

I thought I was handling errors with return files, err but I guess not. Can anyone help me better understand what I should do here?

Don't throw away potential error here stat, _ := os.Stat(path). You should handle it, for example, by returning the error if it's not null, or printing an error message