Golang Panic Crash on Searching Postgres - postgresql

Question

So I have a feature that I want to add in a program I'm writing. Basically, if a user has cookies that say what his username and password are it will look up username and the hashed value of the cookie in a stored postgres database and return a positive response and JWT token if I get a match (made as secure as I can with bcrypt hashing - whether storing hashed passwords is a good idea is maybe another question).
This request is made to the server every time a user goes to a page that requires a saved password.
My problem is that every now and then I get the following
inside CookieLogin
app_1 | search_userinfo_table started
db_1 | FATAL: sorry, too many clients already
app_1 | 2018/08/26 16:22:25 pq: sorry, too many clients already
app_1 | 2018/08/26 16:22:25 http: panic serving 172.21.0.1:37304: pq: sorry, too many clients already
app_1 | goroutine 704 [running]:
app_1 | net/http.(*conn).serve.func1(0xc420156f00)
app_1 | /usr/local/go/src/net/http/server.go:1721 +0xd0
app_1 | panic(0x6d63e0, 0xc420102c20)
app_1 | /usr/local/go/src/runtime/panic.go:489 +0x2cf
app_1 | log.Panic(0xc4200438c0, 0x1, 0x1)
app_1 | /usr/local/go/src/log/log.go:322 +0xc0
app_1 | github.com/patientplatypus/webserver/database.Search_userinfo_table(0xc42017f29d, 0xb, 0xc4201500c0, 0xc4200c22e0, 0xc420043a10)
app_1 | /go/src/github.com/patientplatypus/webserver/database/search.go:18 +0x169
app_1 | github.com/patientplatypus/webserver/authentication.loginHandler(0xc42017f29d, 0xb, 0xc42017f2ba, 0x3, 0x899a80, 0xc420148460)
app_1 | /go/src/github.com/patientplatypus/webserver/authentication/login.go:53 +0x39
app_1 | github.com/patientplatypus/webserver/authentication.CookieLogin(0x899a80, 0xc420148460, 0xc4203fc800)
app_1 | /go/src/github.com/patientplatypus/webserver/authentication/login.go:35 +0x279
app_1 | net/http.HandlerFunc.ServeHTTP(0x75c658, 0x899a80, 0xc420148460, 0xc4203fc800)
app_1 | /usr/local/go/src/net/http/server.go:1942 +0x44
app_1 | github.com/gorilla/mux.(*Router).ServeHTTP(0xc420052460, 0x899a80, 0xc420148460, 0xc4203fc800)
app_1 | /go/src/github.com/gorilla/mux/mux.go:162 +0x101
app_1 | main.JWTHandler.func1(0x899a80, 0xc420148460, 0xc4203fc600)
app_1 | /go/src/github.com/patientplatypus/webserver/main.go:34 +0x342
app_1 | net/http.HandlerFunc.ServeHTTP(0xc4200b12a0, 0x899a80, 0xc420148460, 0xc4203fc600)
app_1 | /usr/local/go/src/net/http/server.go:1942 +0x44
app_1 | github.com/rs/cors.(*Cors).Handler.func1(0x899a80, 0xc420148460, 0xc4203fc600)
app_1 | /go/src/github.com/rs/cors/cors.go:200 +0xe9
app_1 | net/http.HandlerFunc.ServeHTTP(0xc4200b12c0, 0x899a80, 0xc420148460, 0xc4203fc600)
app_1 | /usr/local/go/src/net/http/server.go:1942 +0x44
app_1 | net/http.serverHandler.ServeHTTP(0xc42008a630, 0x899a80, 0xc420148460, 0xc4203fc600)
app_1 | /usr/local/go/src/net/http/server.go:2568 +0x92
app_1 | net/http.(*conn).serve(0xc420156f00, 0x899fc0, 0xc4200506c0)
app_1 | /usr/local/go/src/net/http/server.go:1825 +0x612
app_1 | created by net/http.(*Server).Serve
app_1 | /usr/local/go/src/net/http/server.go:2668 +0x2ce
...and then the golang client will crash and I will have to manually restart. This is an error that happens only sometimes which is incredibly frustrating as it makes debugging difficult (sorry for the verbose terminal log - I'm not sure when the error will fire again).
Does anyone have any advice or suggestions? Is this a common problem with a no-duh solution?
Thanks!
EDIT:
As far as I can tell, here is the offending postgres search query:
package data
import(
"fmt"
"log"
_ "github.com/lib/pq"
)
func Search_userinfo_table(searchEmail string)(bool, string) {
fmt.Println("search_userinfo_table started")
rows, err1 := db.Query("SELECT * FROM userinfo")
if err1 != nil {
log.Panic(err1)
}
for rows.Next() {
var email string
var password string
var regString string
var regBool bool
var uid int
err2 := rows.Scan(&email, &password, &regString, &regBool, &uid)
if err2 != nil {
log.Panic(err2)
}
fmt.Println("email | password")
fmt.Printf("%s | %s", email, password)
if email == searchEmail{
return false, password
}
}
return true, ""
}
Which returns the whether the user is in the database or not as well as the hashed password. Talking with a few people the answer appears to be that postgres adds a new connection every time it makes this read and then eventually crashes, but I want it to reuse connections (although I thought that this happened automagically?). Anyway, more information.

Answer 1

You're missing the required defer rows.Close().
Each instance of *sql.Rows has a connection associated with it. When you close a rows instance the associated connection gets released and put back into the pool (*DB).
Not closing a rows instance, on the other hand, will cause its connection not to be released. And not releasing connections will in turn lead to the connection pool to attempt to open one too many new connections.