Add User to group not working

I tried adding user to a group with below data -
I tried with with and without group id parameter.
I am not able to add the user.
Can anyone can please guide me through this ?

{
"members": {
"d7955967-5d0b-4001-9325-a7900436b8bc": [
{
"userId": "45e03a95-33fd-45e6-9d2f-0f8f82e7f8cc",
"groupId" : "d7955967-5d0b-4001-9325-a7900436b8bc"
}
]
}
}

Output -

{
"fieldErrors": {
"group": [
{
"code": "[missing]group",
"message": "Your request is missing the Group information as JSON in the entity-body."
}
],
"groupId": [
{
"code": "[couldNotConvert]groupId",
"message": "Invalid"
}
]
},
"generalErrors": []
}

There were extra spaces in the URL after member in .../api/group/member___. Issue is resolved.