Http POST request taking lot of time to complete - net/http - Go - post

Question

I am using net/http in Go, and one of my HTTPS POST request is taking lot of time like approx 16 seconds to complete . Though the backend server processing is only taking 2.2 seconds but over all process (when the response is received from the REST API after full processing ) is like 16 seconds .
My call looks like :
https://xxxxx.com/abcded
And the body has a JSON which contains a GIF file base64 of size approx 1.68 MB
{
"username": "test",
"update_username": "0",
"name": "test name",
"isprivate": "0",
"avatar_url": "",
"description": "I am Test , updated using api ",
"location": "test world",
"phone": "12345678",
"age": "23",
"gender": "m",
"update_profilepic": "1",
"profilepic_lat": "28.593",
"profilepic_lon": "77.1981",
"profilepic_height": "480",
"profilepic_width": "480",
"profilepic_type": "photo",
"profilepic": "Dummy String due to Size Constraint in StackOverFlow"
}
Details :
The POST request was invoked from the client (Postman) at 16:59:00.100 But the server recieves the call at 16:59:13.240 (which is shown in the Server logs below) . And finally the server does all the processing and responds back at 16:59:15.073 . And finally I recieved the response code at the client (Postman) at 16:59:15.773
Server Logs Start *****************************************
16:59:13.240
Just Entered into AUTHENTICATION method
16:59:13.246
--------------In Profile Related--------------
16:59:13.246
--------------In Edit Setting--------------
16:59:13.363
---------- In Edit Setting --------
16:59:13.363
Username direct rcvd :%!(EXTRA string=morninglad)
16:59:13.363
Username rcvd :%!(EXTRA string=morninglad)
16:59:13.363
Name rcvd :%!(EXTRA string=morning)
16:59:13.363
Update NON USER NAME UPDATE FLAG RCVD
16:59:13.363
About to call Update Query
16:59:13.374
About to Update the Profile Pic as found the flag
16:59:13.374
Updating the Profile Pic------------
16:59:14.906
About to Insert Media into DB
16:59:14.906
Got the GeoHash :%!(EXTRA string=ttnc9j3tgujw)
16:59:14.952
Found location :%!(EXTRA string=Gurugram)
16:59:14.955
Media Play value is :%!(EXTRA string=)
16:59:14.955
Username :%!(EXTRA string=morninglad)
16:59:14.983
Updating the Profile Pic Done ------------
16:59:14.983
Profile Pic Updated !
16:59:15.041
-------------------Fetch Avatars-----------------
16:59:15.073
The Avatar URL got :Avatar1
16:59:15.073
The Avatar URL got : Avatar2
16:59:15.073
---------- In Edit Setting DONE - END --------
16:59:15.073
--------------Response SENT--------------
Server Logs End *****************************************
So if I go by the above mentioned timestamps ,then time to reach to server was almost 13 seconds , and the total processing time of server was about 2 seconds . And finally recieved the response code in within 1 second.So total time is like 16 seconds for this call.
So I was trying to figure out why the call to reach to server is taking 13 seconds ?
When I am invoking the same call with the smaller body i.e instead of GIF of 1.68 MB to JPEG of 1.4 KB the total time is like 2.2 seconds . So shall I assume that this body size is the reason for increased time ?
But with the kind of internet I am working on (Download speed - 72.33 Mbps and Upload Speed - 6.07 Mbps)this sounds weird .
Any pointer if I am doing something wrong over here ?