Error map
http: superfluous response.WriteHeader call Go: http: superfluous response.WriteHeader call from main.handler (main.go:25)
Go · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (7). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (7)
Go: cannot assign to struct field users["bob"].Age in map
Map values are not addressable, so you cannot modify a field of a struct stored directly in a map.
Go: panic: assignment to entry in nil map
You wrote to a map that was declared but never initialised.
Go: invalid character '<' looking for beginning of value
The decoder received something that is not JSON — often an HTML error page, an empty body or plain text.
Go: listen tcp :8080: bind: address already in use
The port your Go server wants is already taken by another process (or a previous instance of your app).
Go: net/http: request canceled (Client.Timeout exceeded while awaiting headers)
An `http.Client` with a Timeout gave up waiting for the server's response headers.
Go: dial tcp 127.0.0.1:5432: connect: connection refused
Nothing is listening on the host and port your Go program tried to connect to.
Go: assignment mismatch: 1 variable but os.Open returns 2 values
The number of variables on the left does not match the number of values the function returns.
Two steps away (19)
Go: ./main.go:5:2: "os" imported and not used
The file imports a package that no code in that file uses; Go treats this as a compile error, not a warning.
Go: ./main.go:12:2: undefined: handler
The compiler cannot find an identifier — a typo, a missing import, or it lives in another file/package that wasn't built.
Go: ./main.go:18:1: missing return
A function with a return type can reach its end without a return statement on some path.
Go: panic: runtime error: invalid memory address or nil pointer dereference
The program used a pointer, map, interface or struct field that was nil — usually an uninitialised value or an ignored error.
Go: panic: runtime error: index out of range [3] with length 3
Code accessed a slice, array or string element beyond its length.
Go: panic: runtime error: slice bounds out of range [:5] with capacity 3
A slice expression `s[a:b]` used bounds outside the slice's length or capacity.
Go: json: cannot unmarshal string into Go struct field User.age of type int
The JSON value's type does not match the Go field type (string vs number, object vs array).
Go: x509: certificate signed by unknown authority
The Go TLS client does not trust the CA that signed the server's certificate.
Docker: Bind for 0.0.0.0:80 failed: port is already allocated
Another container or host process already publishes that host port.
Error response from daemon: network X not found
The container or Compose project refers to a Docker network that doesn’t exist (any more).
Error response from daemon: Pool overlaps with other one on this address space
Docker tried to create a network whose subnet clashes with an existing Docker network (or a VPN/host route).
Go: Get "https://api.example.com": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
An operation did not finish before its context deadline or HTTP client timeout.
Go: accept tcp [::]:8080: accept4: too many open files / open x: too many open files
The process reached its file-descriptor limit — usually leaked connections, files or response bodies.
driver failed programming external connectivity on endpoint: iptables: No chain/target/match by that name
Docker’s iptables rules were wiped (firewalld/ufw reload, iptables flush) while Docker was running, so it can’t publish ports.
Go: x509: certificate is valid for www.example.com, not api.example.com
The server's certificate does not list the hostname you connected to (SAN mismatch), or it has expired.
Go: sql: database is closed
The `*sql.DB` handle was closed (or the connection died) before the query ran.
Go: ./main.go:9:6: no new variables on left side of :=
`:=` declares variables, but all names on the left already exist in the same scope.
Go: invalid operation: a + b (mismatched types int and float64)
You combined two values of different types; Go never converts numeric types implicitly.
Go: cannot use "5" (untyped string constant) as int value in argument to f
A value's type is not assignable to the type required by the variable, parameter or return value.
Map another error
Popular: 500403400ORA-009331064Critical errorFileNotFoundException assemblyTypeError