从（json）字符串中删除无效字符

I'm am executing a command in a go program which gives me some output with the structure

  c := exec.Command("mycommand")
  stdout, _ := c.Output()

Output

{
 'name': 'mike',
 'phone': '12345'
},
{
 'name': 'jim',
 'phone': '1234'
}, //notice the final comma

To make valid json, I am trying to prepend [ and then append ], and, finally, remove the final comma.

k := "["
mystring := string(stdout)
k += mystring
k += "]"
str := strings.Replace(k, "},]", "}]", -1)

w.Header().Set("Content-Type", "application/json; charset=utf-8")
fmt.Fprintf(w, str)

When I put the final product in a json validator, I get this error

Error: Parse error on line 1:
[{  
---^
Expecting 'STRING', '}', got 'undefined'

Question: is there a way to do json.Compact or something similar on a string, or how can I make valid json in this situation?

Update

this is the output that my coding magic produces. I'm not sure exactly what part of it is invalid

[{
  'name': 'Leroy',
  'phone': '12345'
},
{
  'name': 'Jimmy',
  'phone': '23456'
}]

As JimB pointed out in comments single quotes are not valid json. So if you run another string replace k = strings.Replace(k, `'`, `"`, -1) to produce this;

[{
    "name": "Leroy",
    "phone": "12345"
}, {
    "name": "Jimmy",
    "phone": "23456"
}]

Then it should work as you expect.