Can't get autocompletion with cargo

[trayanr]

Racer doesn't show lool up definitions in $CARGO_HOME

rustc 1.42.0 
cargo 1.42.0 
racer 2.1.31
RUST_SRC_PATH = /home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src
CARGO_HOME = /home/trayan/.cargo

Cargo toml:

[package]
name = "gtk"
version = "0.1.0"
authors = ["trayan"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

[dependencies.gtk]
version = "0.8.0"
features = ["v3_16"]

[dependencies.gio]
version = ""
features = ["v2_44"]

I ran cargo run to generate the .lock file.
Now if I run RUST_BACKTRACE=1 RUST_LOG=racer=trace racer complete std

DEBUG 2020-03-21T11:54:03.945489284Z: racer::util: Getting rust source path. Trying env var RUST_SRC_PATH.
DEBUG 2020-03-21T11:54:03.945551380Z: racer::nameres: do_file_search with search string "std"
DEBUG 2020-03-21T11:54:03.945560597Z: racer::util: Getting rust source path. Trying env var RUST_SRC_PATH.
DEBUG 2020-03-21T11:54:03.945571187Z: racer::nameres: do_file_search std_path: Some("/home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src")
DEBUG 2020-03-21T11:54:03.945587388Z: racer::nameres: do_file_search v: ["/home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src", "."]
MATCH std,1,0,/home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/lib.rs,Module,std

But running RUST_BACKTRACE=1 RUST_LOG=racer=trace racer complete gtk results in:

DEBUG 2020-03-21T11:54:57.536131170Z: racer::util: Getting rust source path. Trying env var RUST_SRC_PATH.
DEBUG 2020-03-21T11:54:57.536201101Z: racer::nameres: do_file_search with search string "gtk"
DEBUG 2020-03-21T11:54:57.536211952Z: racer::util: Getting rust source path. Trying env var RUST_SRC_PATH.
DEBUG 2020-03-21T11:54:57.536223513Z: racer::nameres: do_file_search std_path: Some("/home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src")
DEBUG 2020-03-21T11:54:57.536245675Z: racer::nameres: do_file_search v: ["/home/trayan/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src", "."]

It would seem that racer doesn't look in the cargo directory, so it doesn't find the definitions. Can I manually add it from the command line?