Runtime error: "assignment to entry in nil map"

I'm trying to create a slice of Maps. Although the code compiles fine, I get the runtime error below:

mapassign1: runtime·panicstring("assignment to entry in nil map");

I attempt to make an array of Maps, with each Map containing two indicies, a "Id" and a "Investor". My code looks like this:

for _, row := range rows {
		var inv_ids []string
		var inv_names []string

		//create arrays of data from MySQLs GROUP_CONCAT function
		inv_ids = strings.Split(row.Str(10), ",")
		inv_names = strings.Split(row.Str(11), ",")
		length := len(inv_ids);

		invs := make([]map[string]string, length)

		//build map of ids => names
		for i := 0; i < length; i++ {
			invs[i] = make(map[string]string)
			invs[i]["Id"] = inv_ids[i]
			invs[i]["Investor"] = inv_names[i]
		}//for

		//build Message and return
		msg := InfoMessage{row.Int(0), row.Int(1), row.Str(2), row.Int(3), row.Str(4), row.Float(5), row.Float(6), row.Str(7), row.Str(8), row.Int(9), invs}
		return(msg)
	} //for

I initially thought something like below would work, however that did not fix the issue either. Any ideas?

invs := make([]make(map[string]string), length)

You are trying to create a slice of maps; consider the following example:

http://play.golang.org/p/gChfTgtmN-

package main

import "fmt"

func main() {
	a := make([]map[string]int, 100)
	for i := 0; i < 100; i++ {
		a[i] = map[string]int{"id": i, "investor": i}
	}
	fmt.Println(a)
}

You can rewrite these lines:

invs[i] = make(map[string]string)
invs[i]["Id"] = inv_ids[i]
invs[i]["Investor"] = inv_names[i]

as:

invs[i] = map[string]string{"Id": inv_ids[i], "Investor": inv_names[i]}

this is called a composite literal.

Now, in a more idiomatic program, you'd most probably want to use a struct to represent an investor:

http://play.golang.org/p/vppK6y-c8g

package main

import (
	"fmt"
	"strconv"
)

type Investor struct {
	Id   int
	Name string
}

func main() {
	a := make([]Investor, 100)
	for i := 0; i < 100; i++ {
		a[i] = Investor{Id: i, Name: "John" + strconv.Itoa(i)}
		fmt.Printf("%#v\n", a[i])
	}
}