如何在make（）语句之前确定可用内存

In Go, when using a make statement, for example, allocating megabytes of memory

    make([]byte, 1024*1024*d)

Is there a way to determine how much memory is free, before asking for more memory?

Yes there is. You can use the gopsutil package:

package main

import (
    "fmt"

    "github.com/shirou/gopsutil/mem"
)

func main() {
    vm, err := mem.VirtualMemory()
    if err != nil {
        panic(err)
    }
    fmt.Printf("Total:%d, Available:%d, Used:%d", vm.Total, vm.Available, vm.Used)
}

There are also lots of ways to get this information that are OS-specific. None of them are perfect, but they'll give you something.

You could also have Max Memory as a configuration variable and use: http://godoc.org/runtime#MemStats.

Thank you for all your input.

I have decided to use a Max_Memory configuration option, since the use case for this is to utilize n Megabytes of memory up to about 75% max available, on test servers, which are only running this application, as a way to trigger autoscaling in a test environment.