Can't determine the nature of こう in this sentence


Here's the quote :

> 「三人で手をつないでこうね。」

The context is "three frogs are taking hands and are ready to go for a walk".

At first I thought こう here meant "let's go" but that would be いこう right?

The other possibility could be the adverb こう (more often そう) in which case
it'd mean `"they took each other's hands and like that [they went for a
walk]"` implicitly referring to the verb in the previous sentence.  
I've never seen this grammatical construct before.

Therefore I am not sure what's the precise meaning here, plus it's quite an
old book I guess so It could also be an expression that is not used anymore.
What do you think?




It is a colloquial contraction of いこう, only found in the form of verb + いこう →
verb + こう (so not in a place of a stand alone 行こう, as far as I know). It can
also be こー or just こ. As far as a colloquialism goes, it's more of a childish
one than a slang-ish one.

An old song (1998) by Puffy has this line:

> 車で 駆けてこ

It is a contraction of 車で駆けていこう. (The song is called 渚にまつわるエトセトラ.)

As a more recent example, I found this pattern used in [a PR
phrase](https://www.nisshin-
oillio.com/company/news/down2.php?attach_id=1098&uid=6324) (2020):

> 「鮮度のオイル、かけてこー」

The last part is a contraction of かけていこう.

