Out of memory when transferring large file - go

Question

I'm using Go Gob to transfer large files (~ 1 GB) or many small files (~ 30 MB). Server is running in a loop, and will receive files when clients send it.
My code is working if I send one large file, or few small files, but when sending a large file for the second time, it returns a 'fatal error: runtime: out of memory'. If I send a large file, stops the program, then starts again and send another large file, it works.
It looks after receiving file via Gob and writing into a file, it is not releasing memory.
Server code
type FileGob struct {
FileName string
FileLen int
FileContent []byte
}
func handleConnection(conn net.Conn) {
transf := &FileGob{}
dec := gob.NewDecoder(conn)
err := dec.Decode(transf) // file from conn to var transf
if err != nil {
fmt.Println("error to decode into buffer:", err)
}
conn.Close()
file, err := os.Create("sent_" + transf.FileName)
if err != nil {
fmt.Println("error to create file:", err)
}
file.Write(transf.FileContent) // writes into file
fileStat, err := file.Stat()
if err != nil {
fmt.Println("error to get File Stat:", err)
}
file.Close()
fmt.Printf("File %v was transferred\n", transf.FileName)
fmt.Printf("Transferred: %d, Expected: %d\n", fileStat.Size(), transf.FileLen)
}